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spin-1/2-nuclei

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Everything posted by spin-1/2-nuclei

  1. Hello, The equation for the equilibrium constant is given in stage 6. That is what you need to answer your question. From looking at that you can see that you will need to know the concentrations of both the reactants and the products. Now, the concentration of the reactants is easy to know, but how will you determine the concentration of the products? Since this is homework I will give you some hints. Hint # 1: A titre describes the mass of one compound that reacts with 1mol of your solution. Hint # 2: The mechanism of the above mentioned reaction: (I debated spelling this out, but I think it is best if you try it first yourself - so please try it and then if you get stuck or need me to check it I will) Hint # 3: Sulfuric acid is used as both a dehydrating agent & catalyst in the esterification. Since the esterification reaction is reversible the only way to drive the reaction forward is to remove water. Hope this was helpful... Cheers
  2. Uh, yeah I remember my first science kit, and it never had anything dangerous in it. So like I said, if someone wants to learn how to make rock candy I'm more than happy to oblige. As far as your other statements go, I don't even know where to start. You do realize that training and certification are necessary for a reason right. Would you go to a "doctor" with no proper training? I mean wow, just wow. I suppose requiring me to have proper training before performing brain surgery on my neighbors would be "squelching curiosity" too. LOL! sigh..
  3. "For someone who claims" to be an analytical chemist - you've surely never taught or taken an undergrad lab in your life. There is a reason training is required in specific fields, and to suggest otherwise is downright ridiculous. You can sit at home and safely draw mechanisms for reactions or model transition states on your computer and satisfy all the curiosity in the world. There is no need for an amateur to be attempting extractions on anything. Undergrads, graduate students, and some MS/PhD chemists have accidents in the lab... Distillation labs come to mind, I've seen more than one undergrad set their apparatus ablaze due to lack of greasing joints despite directions about how not to set your distillation on fire being placed in the lab manual, their text book, and also told to them directly in pre lab (shrugs), graduate students lighting their oil baths on fire because not everything can be used at as an oil bath at every temp (who knew? a properly trained chemist would) - oops - graduate students prepping THF stills and blowing out the back wall of their lab, accidents with dropping argon cylinders and blowing out walls, incorrectly refilling the liquid nitrogen dewar for the laser, use of t-butyllithium in halogen metal exchange exposing it to air because the syringe/needle set up was done improperly and argon pressure blew the back off (that student caught themselves and the bench top (stacked full of reagents) on fire, another unfortunate girl at UCLA died from something similar while working over the christmas holiday (she was inexperienced and working without guidance) she had a B.S. in chemistry and was working towards a PhD, improper use of vacuum pumps resulting in exploded glassware, attempting to rotovap diazidomethane (boom) due to improper identification of all reaction products, inhalation of some or other form of very bad gas from doing chemistry (incorrectly) on the bench top instead of the hood, accidents related to inhalation of ether whilst running a column on the bench top instead of the hood, the list goes on.. and these were all "trained" chemists of varying degrees in university labs. - http://www.chemistry-blog.com/2009/01/20/tert-butyllithium-claims-fellow-chemist-at-ucla/ - http://pubs.acs.org/cen/news/88/i27/8827news3.html Chemistry is not a hobby it is a profession, if people want to do hobby chemistry then they can ask me how to make rock candy or polymer and I will be happy to oblige. I'm not telling people how to make meth, extract magnesium, or synthesize precursors to controlled pharmaceuticals more powerful than morphine. This kind of stuff reminds me of the ultralight and glider "pilots" and even some private "pilots" coming to me for their airport safety check before renting or FAA required biannual checkout in the case of the licensed pilots.. Most pilots (of all experience levels) are safe, but there are always a few moaning about all the "unfair" training regulations put forth by the FAA, because god forbid anyone actually be competent before being allowed to enjoy their hobby (now-a-days society is so restrictive, always violating ppls rights by not allowing 10 year olds to have drivers licenses, etc). Flying is NOT a hobby, inexperienced pilots crash often, they bust controlled airspace and endanger civillian and military aircraft often... They f'up instrument approaches in actual instrument conditions because they have no current training, often. If someone is unwilling or unable to actually take the time to learn a particular skill correctly but they are curious about said field anyway - that does not excuse them from the rigors required to be competent in said field... If you like chemistry read a book about it - get one of those chemistry sets with detailed - safe - experiments already listed in them. If you like flying - go to the aviation museum or whatever.. but you don't do complex chemistry in your basement/garage with no training (note I didn't say formal training - I said no training) and you don't get in your C-150 and fly out into the eye of a thunderstorm with 1 mile of visibility and rusty instrument skills due to 3 hours of flying logged in the past 365 days. If you've actually read any of my posts here, you'd know that I spend a lot of time helping curious people. Truly curious people are happy to have a general answer to their question, without needing details to attempt procedures that are potentially unsafe. Pretty much everyone else either wants a HW assignment completed (in which case I could object for multiple reasons), or they are planning to do something potentially dangerous in their parent's/their own garage/basement... To each his own - I prefer safety first.. You are of course free to use your training however you see fit (in which case you'd be better served answering the question yourself instead of lecturing me about my chosen safety practices, as those will not be changing any time soon).. Cheers
  4. Nope. I agree. Why can't people make rock candy when they decide to take up chemistry as a hobby? It's tasty, safe, and you can make it in many pretty colors! sigh..
  5. I think I have a different definition of what non-compatible means. I see people trying to ask others to explain their religious beliefs with logic and expecting implementation of the scientific method to justify their beliefs. When people are basing their belief system on faith or feelings, it's not really possible to apply the scientific method to that. As I see it, this is the problem that occurs in these debates. Feelings and faith are subjective, they cannot be quantified scientifically... So asking someone to justify a feeling or something based on faith is not really scientific - at least in my opinion. I mean what is the pH of a feeling? How faithy is one person's faith compared to another? Regarding your other statements, you can hypothesize about a god as much as you like but all the quantum mechanics in the world is not proof of his/her/it's existence... thus at this stage hypothesizing is fine & you are of course free to do that, but to call it scientific is a stretch. I could dream up any manner of things and retroactively explain them via scientific observations. This is called researcher's bias. It is far better to find evidence of something that suggests a god and then via experimentation and observation, quantify and describe the god like phenomenon and once all data is acquired figure out what is going on from there. If the data suggests a god then we get "the theory of god like thingy" and if it doesn't we get more unexplained stuff that tells us we are observing something different, but not exactly why. That's just my two cents.. Cheers
  6. Hi all What spin said already covers the basics. The rest depends on the compound details. Since you're familiar with silica columns you will catch on quick. Look at this book: Preparative Chromatography Techniques: Applications in Natural Product Isolation by K. Hostettmann, Andrew Marston and Maryse Hostettmann (Dec 7, 2010) & you will be an expert in no time.
  7. Unfortunately, as I see it, these discussions about religion always end the same way. The agnostics/atheists using science to back up their perspective and the religious people using faith, the bible, and other such religious texts to back up their perspective. Through all of it, nobody ever seems to realize or accept that these two things are simply not compatible. That isn't to say that religious people cannot be scientists, but rather that you cannot (at least at this time) use science to justify or disprove the question "is there a god". People also fall into the trap of negative evidence, and causation vs. correlation. It is hard to deny that specific events listed in the christian bible have been debunked - now I have a friend who is a devout catholic and also a physicist - and simply compartmentalizes religion and science. When I ask him as a man what he thinks about the age of the earth, the bible, and carbon dating he will simply say - "the things that happen in the bible as they are explained are not for him to question or debate and perhaps we have misinterpreted them", and when I ask him as a scientist what he thinks about the age of the earth the bible, and carbon dating he will simply say - "There is no way the earth is as young as has been suggested in the bible and other religious texts".. I always wondered how he was able to reconcile these things in his mind. I personally don't believe in religion at all, but I have to admit that when I view his position with an open mind, his approach to this seemingly paradoxical existence actually makes sense. If he accepts that god cannot be explained by mankind and neither can the claims made about him or his creations in the bible (not my personal view but that is not the point of this discussion) then the fact that we've proven or disproven something that occurs or is said in the bible with manmade technology (that he readily admits holds valid for the world as we observe it - which is where science belongs) is really of no consequence to him - from the perspective of his faith based belief... and honestly, if I am viewing this objectively, I really can't fault him in this and calling him illogical is simply unfair. I have no opinion about religion one way or the other - accept that I personally chose to stay away from it - but then again I don't form opinions about things that I cannot readily observe as a personal policy, but that doesn't really make my manner of thinking superior to anyone else's. Depending on the person, there is value in adopting either position or - in my case - none at all. Cheers
  8. I've already stated that I personally plan to adopt, but I don't consider adoption or even abortion quite the same thing a eugenics. I have no moral objection to abortions for any reason - so long as said abortions aren't being forced on the person/couple via public policy to preserve the "purity" of the gene pool. I think we should focus more on keeping people that are already here alive - i.e. anti-aging technology etc - than we should on moving the aged population (typically those with the most knowledge and experience) out of the way just to get more people born each year. I think quality rather than quantity should be more important. What we need is a balance between birth rate and death rate so that population control is not something that has to be forced on society.. and certainly even if it is - it should never be in the form of eugenics. That is my opinion. Thus, I think if - for example - people start living to 150 years and can live well thanks to modern medicine - that isn't a bad thing - can you imagine another 70 years with someone like Einstein contributing... obviously people hooked up to life support machines indefinitely is not an option, nor am I advocating that, but I do think finding a way to prolong human life (usefully) and cure illness and disease - are worth the costs.. Well, I disagree with this. Ignorance can be combated with education, but you can't tell a stupid person anything, by their very nature they are rigid in thought and do not readily respond to reason. Now that, in my opinion, is a major waste of resources.. Sheeple don't tend to respond to reason - it's actually quite alarming. Willful ignorance can often come off as stupidity, but again I maintain that those are not the same. Ignorant people can obviously benefit from education, but I think there are a great deal more selfish, hatefilled, violent, and intolerant people than you realize (all of those people - as far as I'm concerned - fall under the category of stupid because they absolutely will not respond to reason) They already KNOW they are right due to their rigid thinking - you are not impacting those people no matter what you do. They respond to force and violence - but those aren't really options because that is not humane.. and as I said before - human civilization devoid of all it's humanity - as far as I'm concerned - is just a waste.. Yet, as I said before, those people (stupid people) have been plaguing mankind since we started walking upright and they will continue to do so for the rest of time as far as I'm concerned.. I really don't think any amount of education will do much for people like that. I'm pretty sure most of the germans supporting the Nazi agenda back in the day were well educated at the primary school level, at least in the basic first principles, and many of the Nazi scientist [Haber comes to mind] were certainly well educated and yet they were still quite stupid. I mean that guy hated on his own people? Strange.. So much devastation and destruction and for what? Because Jews were genetically inferior? Well, Einstein is proof that this was surely not the case.. Thus, as I see it, there are some things that education can't teach - tolerance is one of them - and many people (those people I like to call stupid people - don't have an ounce of tolerance and from my experience can earn PhDs in the hardest subject you can think of and still not obtain it).. Socially forced eugenics is not the answer in any situation, even for people such as those mentioned above, that is my personal opinion. The only way to combat people like that is to legislate away their power. Isolating their views and harmful assertions from society and thereby protecting it via wrapping those people up tight with saran wrap is really the only way to do it. Then they can sit in their little plastic rooms tossing poo all over the place with no physical harm coming to innocent bystanders.. If someone wants to hate Jews - fine - but it shouldn't be allowed to go any further than whatever they envision in their own head.. There are some things that should never be allowed under any human government. 1. slavery, indentured servitude, military drafting 2. genocide 3. forced segregation (including institutionalized class separation) 4. discrimination of any kind in regards to: race, gender, sexual orientation, looks, intelligence level, and any other innate properties of humans that cannot be controlled by the individual. 5. thought policing should be prohibited in all of it's forms (i.e. religious freedom, artistic freedom etc should always be protected). 6. propaganda should be removed from all forms of government campaigning and government sponsored schooling. I'm sure there are more things, but I think the point is well expressed at this stage. Cheers
  9. Yes you are right, you can use the alumina columns but unfortunately there are some disadvantages to doing so and I personally prefer the silica adsorbent for my columns (but as you said yours are sensitive to silica so that is a bit of a bust).. Still, some people in my lab have had success with these.. Some things to keep in mind though.. For starters, you must mind the water content, since the polar sites will go down with increasing water content - so solvents like MeOH start to become problematic with alumina adsorbent. When you purchase your alumina you'll have to chose the activity (from 1 - 3 and acidic, neutral, or basic), which is just another way of describing it's water content. In our lab we buy activity 1 and deactivate it with water as necessary and as with silica you have to also mind your mesh size in comparison to your chosen flow rate. I have a good reference on using alumina columns with alkaloids somewhere, but I cannot find it on my desk at the moment - so I will have to try to search for it later. I will post here with it again if/when I find it.. Cheers p.s. if I can't find this reference I will ask my lab mate to come here and post an overview of these columns for you.
  10. You've misunderstood me - there is no internal struggle here. I personally value intelligence over looks or physical ability. I've never said that other people should too. The entire point of my post is simply that we are stuck with all kinds of "defective" people because that is what makes humanity "human", and there is no point in preserving humanity if we are going to lose that aspect of ourselves, at least from my perspective. Thus, to be more clear, I think we should live and let live. I personally think the explosion of stupid people in society is alarming, but I never suggested these people should actually be exterminated.. there is no internal struggle here.. In fact, the entire point of my post is that they shouldn't, and more importantly that whomever wants to start arbitrarily assigning "value" to humans will in fact be wandering down a slippery slope. Trust me, I have no risk of low self esteem or low reproductive value in my own eyes. My self esteem is fine because I prefer to link my self esteem to things I am actually good at doing [trying to help people less fortunate than me, taking care to place my friends and family members first whenever possible, being a good scientist, being a good pilot, being okay at motorcycle racing, etc, etc], thus I avoid wishing for other people's skills and/or trying to be other people. We are all different.. As far as my reproductive "self esteem" goes. I don't plan on having children - ever. I've had a rather difficult life [despite coming from a rich family] since the choices I've made [joining the military to get combat flight, working as a medevac pilot, volunteering my time in Africa for AIDS and TB related research after learning that qualified researchers with my computational background are hard to come by in these parts of the world] have exposed me to many of the darker sides of humanity, and since I'm personally unhappy with the way the world is going right now I have decided not to have kids of my own. Thus, I will simply adopt children once I have completed my postdocs/obtained tenure/or landed a stable industry job. There is no need to add an additional life to this planet when there are so many unwanted little kids suffering right now as I sit here and type this message. So, in short, Thinking that stupid people will be the downfall of mankind - as I see it - is perfectly reasonable (we are all autonomous individuals with rights to our own minds).. I never said exterminating stupid people is appropriate nor do I have any internal struggle about this issue - but personally, I cannot deny that fanatics of all types (stupid), racists/intolerant/bigoted/hatefilled people (stupid), violent people (stupid), selfish people (stupid) will be the downfall of mankind. So when I hear people moaning about the gene pool and worrying that allowing a few sick individuals to live will be the demise of mankind I have to laugh a little - because I think we will take ourselves out just by being ourselves - (since there are more stupid people than there are smart people)... I also think you are confusing stupid with ignorant. I said that stupid people will be the downfall of mankind - (i.e. people who think they know everything, know nothing, make no attempt to learn anything about what they don't know, and form opinions and positions (that to them are the word of God) solely from their own preferences with no regard to the validity of their position when viewed objectively, nor a care given to the thoughts, feelings, rights, or preferences of anyone else) - not ignorant people.. As I see it, there is a huge difference between those two.. stu·pid/ˈst(y)o͞opid/ Noun: A stupid person (often used as a term of address): "you're not a coward, stupid!". Adjective: Lacking intelligence or common sense. vs. ig·no·rantAdjective/ˈignərənt/ 1. Lacking knowledge or awareness in general; uneducated or unsophisticated. 2. Lacking knowledge, information, or awareness about something in particular: "ignorant of astronomy". Cheers
  11. I think you've misunderstood. It's not wasteful because you don't need more ET3N than you normally would, you just run it through without the rest of the solvent - i.e. - you push it through alone. So the volumes between the two methods are very similar. I typically add 1ml of ET3N for every 5 to 6 grams of silica gel. This is why you must use the air to push this through. I simply keep collecting that ET3N and redistributing it through the column. When I get to the 3rd or 4th run and it seems like the silica has been mostly wetted with it, I add the solution made up for washing/packing the column. Typically in my case petroleum ether. I then run that through the column a few times and clean out the ET3N - since the silica is already deactivated I don't need excess ET3N hanging around and messing up my separation. This procedure always works well for me when I am working with alkaloids and polar amines, but everyone has their own preferences. I prefer to dry pack because I run columns on both micro and large scales. I've found that for me, dry packing works best with both, but is an absolute must for microscale columns. They're easier to set up, there is less mess (no residue hanging out on the side walls of the column), it is easier to control the exact height of the silica gel in the column (which is paramount for me), and if you know what you're doing you can get these columns evenly packed and cracked free easily. but, no matter which method you decide to use, you will find many many experimental procedures for purifying polar amines if you check Sci-Finder and grab some SIs. Cheers
  12. Hello, Have you tried reverse phase HPLC? If not, you can spray your TLCs with ET3N prior to use.. Also, when working with amines you must first wash your silica with ET3N prior to use. I typically dry pack my columns, push them down with air (before adding compound and sand at the top) and then run the ET3N through the column a few times, since I dry pack this has to be done until the column is fully saturated. I then push the excess ET3N out with air - but am careful not to dry out the silica - then I add my solvent system as normal.. This always works great for me whenever I have to deal with alkaloids. Get on Sci-Finder and grab some SIs for papers that have a synthetic route containing an alkaloid or other polar amines. Some of them will have good procedures for purifying all manner of polar amines and alkaloids. There are many procedures - some that involve the use of ET3N washed silica etc as I described before, and some use buffers in mobile phase with pHs typically ranging from 8 to 12. There are too many methods to try to describe them all here (especially from memory) and I'd hate leave something out and mess you over - so, if my above method doesn't seem like it will work for you - or if you have already tried something like it - time to dig in and read a bunch of SIs.. Unfortunately, running columns on amines and alkaloids is a lot like black magic. You bubble a little of this, add a little of that, spin around on your head a few times, sacrifice an undergrad or first year [if you are either my apologies (and you will need to find a premed major ;-)]clap twice to the east - and hopefully you get good results.. If you really need more info on how chromatography works, I'd be happy to walk through that with you, but I am assuming (please tell me if I'm wrong) that you were just being facetious.. Either way, Best of luck, you have my sincerest sympathies.. Cheers.
  13. This is a good question. Personally I don't think we have much need for a "human" race devoid of all it's humanity. Eugenics is inhumane for a multitude of reasons. I think the human gene pool will survive. The biggest threat to us is not the people with genetic disorders being kept alive by modern medicine (I think many of them would chose not to procreate if medical professionals took the time to explain the risks to their children) but rather all of the random stupid people left to run rampant and bring chaos to all. Stupid people procreate - and they often have stupid children (either as a result of nature/nurture/ or a combination thereof), these stupid people ruin the environment, vote, and in general bring down the overall IQ of the human race. So much energy and effort has to be placed into dumbing things down for these intellectually challenged individuals and they rarely respond to reason. Should we exterminate everyone with a crappy IQ? Surely dumb people are doing more damage to the human race than people with "defective" genes that cause illness.. Personally, I think if we want to remain human, we are stuck with both. As soon as we start trying to quantify the value of a human life based on some arbitrarily selected parameters - trust me if this goes to a vote being Paris Hilton will probably count more than being Stephen Hawking (if you don't believe me watch the Jersey Shore, and then ask yourself how it is possible that there are enough people out there interested in something like that show, for that show to get enough ratings for you to even be able to watch it) - that is when we've lost the plot.. At some point population control will probably have to be implemented. I think there will come a time when fewer babies have to be born in order to sustain mankind - although - if we start trying to utilize eugenics to ensure the genetic "purity" of said babies I think we will have gone down a slippery slope that will be far more damaging to the human race than any addition of "defective" genes in to the gene pool could ever be. I think prejudice, intolerance, and uncontrolled capitalism will take out humanity long before any "defective" genes do.. just my two cents.. Cheers
  14. Hello Finiter, I understand where you are trying to go with this, but unfortunately, you cannot separate work being done during compression from the kinetic energy of the system nor can you (via any stretch of the concept or even the definitions) create proportional relationships between system properties that simply - due to the nature of the system - cannot exist. There is no alternative concept outside of work from which you can relate the increase in kinetic energy of the system following compression. Objects fall due to gravity - there is no other source from which to derive this behavior.. This is what observation tells us, just as observation tells us that work done on the system when it was compressed increased the kinetic energy. The how that happens is just as important as the why that happens. This goes back to the concept of for every action there is an equal and opposite reaction. In it's most basic form, physics is the science of quantifying actions and their corresponding equal and opposite reactions such that energy and matter are accurately described and always conserved. Thus, sticking to the law of conservation of energy - you cannot have an increase in kinetic energy without some kind of change, the increase in kinetic energy would be the reaction to the action (compressing the system via work) in your example. Yes, you can redefine heat - as in you can use heat to describe whatever you want so long as an appropriate legend accompanies your definitions, but in this case you are not only redefining heat - you are also confusing the concepts. That is to say the word for heat in german is not heat - but while the concept is called something different - the mathematical representation of it remains the same. In your case you are trying to redefine the math. You are stating that work done on the system does not in fact result in the increase in kinetic energy - that this increase can be explained by something else.. this is not a difference in definitions being used, but rather a completely different description of the system. Hope this was helpful, Cheers
  15. Hello, The Markonikov vs. anti Markonikov products are examples of what is called regiochemistry. The Markonikov vs. anti-Markonikov product is formed depending on where the most stable carbocation or radicle will be formed during the intermediate of the reaction. Thus, The Markonikov vs anti-Markonikov product depends on which mechanism the reaction is undergoing... In the case of radical addition or hydroboration you have a situation where the opposite regiochemistry results from the inversion of the order of steps in the mechanism. In the case of the anti-Markonikov product... After the initiation step to form the X radical with whatever random initiator, the X radical - in your case Br, will (via the fishhook arrows for pictorial representation) propogate via formation of a bond with one electron from the double bond of the alkene and the other electron from the double bond of the alkene will go to form the most stable radical... That is to say that, the radical will be on the carbon with the most substituents. To obtain your product the radical will then propogate with another H-Br [H-X] by again forming the most stable radical. Thus the bond between the H and Br, consisting of two electrons, will send one of it's electron with the hydrogen to form the H-C bond and quench the radical (producing your anti-Markonikov product). Now, the new radical just formed, the Br radical (being the most stable), will go on to another propogation step with another alkene. termination can occur between any two radicals, but no new radicals will be formed during that step. Do not confuse the propagation with termination step. *Note that the rate between propogation between the alkene radical and an H-Br molecule will be faster than the rate for propogation between an alkene radical and an alkene. This is because of sterics, etc. So the reason you get the different regiochemistry -i.e. anti-Markonikov - arises from stability of the intermediate.. So review a good source on radical mechanisms and this will make more sense.. remember your three steps in a radical reaction are 1.) initiation, 2.) propogation, and 3.) termination. Also review radical stability. In normal Markonikov addition - you are typically forming a carbocation - which will always form on the carbon with the most substituents. Then you will have attack of a nucleophile (I can go over what makes something a good nucleophile with you in another post if you wish) So, in the mechanism to produce Markonikov regiochem, the alkene will use one of it's bonds to deprotonate H-Br. The reason the hydrogen is "grabbed" first is because it is less stable as a H- than Br is as a Br- (if you don't understand why I can go over what makes something a good nucleophile and likely to hold a negative charge and other such concepts that will make this more clear) but, for now - if you don't understand Hard Soft Acid Base theory - let's just accept that the hydrogen is grabbed because it is less able to exist unbonded/with a negative charge than the Br is.. Now that you have the carbon hydrogen bond formed, formal charges tell us that the carbon opposite the carbon that received the hydrogen is now missing a bond and therefore has a positive charge.. primary carbocations are less stable than secondary carbocations which are less stable than tertiary carbocations. (I can go over all of this with you in another post too if you need but for now we have to accept at face value that, during reactions the most stable carbocation will typically form). Thus, the hydrogen will go to the least substituted carbon of what used to be our alkene and as a result a positive charge must be assigned to the carbon best able to support it - i.e. - the carbon with the most substituents. Then, the Br- (being the nucleophile in this situation) will attack the positively charged carbon and the Markonikov product is formed with the Br on the most substituted carbon. So, in the radical reaction that gives the anti-Markonikov product - the Br is delivered to the least substituted carbon because during propogation it needs to make a bond and it cannot make a bond with the most substituted carbon - because that carbon needs to take the other electron from the alkene bond and thus place the radical on the most substituted carbon.. In the Markonikov product the mechanism undergoes a carbocation - which forms on the most substituted carbon and it is the carbocation that is attacked by the Br in this case. Hopefully this was helpful.. Cheers..
  16. Yes, it is difficult to obtain chemicals as a private individual in the western countries. Cheers
  17. Hello, If you're a business or working at a university you can easily get an account with major chemical suppliers like Aldrich, etc. They will not sell to you if you are not a legit company/university with a legit need for chemicals etc. - http://www.sigmaaldrich.com/chemistry.html?cm_mmc=Google_eBusiness-_-search-_-SIAL+Branded_Aldrich+Chemicals-_-aldrich_Phrase&cm_guid=1-_-100000000000000025735-_-7408516959 If you are a private individual not involved in a business, it will be very difficult to obtain access to chemicals for personal use. If, on the other hand, you have a PhD in a relevant science - or the person who is/would be working for you does, you may be able to coordinate access to hood/lab space at a local University's tech park (if they have one), but you will need legitimate research and reasonable startup capital. Otherwise, you can rent industrial lab space etc, but again, you will need someone with a PhD or MS and a few years experience in charge of your lab and capital before you are likely to gain access to a space to work and chemicals to stock it with. hope this was helpful, Cheers..
  18. Hello Finiter, not if you're suggesting that the increase in temperature - which is a result of the increase in kinetic energy - doesn't come from the work done on the system during compression. The act of compressing does do work on the system and hence increases the kinetic energy, which in turn increases the temperature... Since internal has many other parts, not just kinetic energy - it is impossible to tell the total internal energy of a system from the increase kinetic energy alone. Yet, if there is an increase in temperature there MUST be an increase in kinetic energy, however the same is not true for the internal energy. One can say that if there was an increase in the specific heat - i.e. how long it will take to increase the temperature of 1kg of the substance in the system by 1k or in the case of heat capacity the entire system, one can then say that there may have been a change in internal energy (but even this will not quantify an exact relationship between the internal energy and the increase or decrease in time it takes to warm a system or cool it. Now, that doesn't mean that temperature and internal energy are not related but rather that they are not directly proportional and thus you cannot get the kind of information that you want about the internal energy from the temperature. Hope this was helpful, Cheers..
  19. No - not necessarily - see the links I provided in the posts I gave before. The temperature is only directly proportional to the kinetic energy. The internal energy is comprised of both kinetic energy and potential energy. So in this case one container relative to another - one of them under isothermal conditions to keep both containers at constant temp (they are at constant mass), the pressure produces a different concentration of the gas - and therefore a different chemical potential.. Thus in this case both containers are at equilibrium, yet they do not have the same internal energy when an equal amount of reactant is introduced into both containers because their chemical potential is different despite the fact that their temperatures, and masses are the same. So the same kinetic energy but different internal energy.. So, you can relate the chemical potential with temperature mathematically (lagrange multiplier for average particle constraint in a system during maximization of entropy), but this does not mean that the temperature describes the internal energy of the system (even at equilibrium).. it does not.. temperature is directly proportional to kinetic energy not the internal energy.. In the Gibbs free energy equation.. deltaG=deltaH-TdeltaS temperature is related to the change in the entropy of the system.. To better understand this situation, you can look at chemical potential like gravitational potential.. If I have two 100kg balls and place one of them at the top of the hill and another one of them on a completely flat surface they will have different potential energies. Since in molecules the internal energy includes chemical potential the configuration of the molecule must be taken into consideration.. both the position of the molecules relative to other molecules as well as the literal molecular configuration. This changes with environment. That is to say that not all equilibrium conditions for one set of reactants will produce the same internal energies for said reactants if/when they are placed in conditions to react with another substance.. Some reactions have multiple reaction pathways - as in they can undergo many different mechanisms - which will produce different transition states of different energies, and depending on what conditions you hold constant at the previous equilibrium prior to the reaction beginning - i.e. - depending on where you hold the equilibrium values at, you can in fact get very different products with different stability. Since chemical potential describes how likely a chemical transformation, phase change, or configurational change is to take place, talking about internal energy while excluding the chemical potential is a lot like talking about the total energy of a 100kg ball absent of it's position - i.e. - in exclusion of it's location.. hopefully this was helpful.. Cheers..
  20. @Finiter *note above I meant to say the temperature doesn't tell us much about the internal energy... sorry if that caused any confusion.. working long hours here - and I don't always have time to proof read my posts.. sorry.. Cheers.
  21. Hello Finiter, In this case it is the concentration that controls the rate of the reaction, and the concentrations are different because the pressures are different. This is because mass and concentration are not the same thing although they are related. Another thing to note, is that since internal energy is both kinetic energy and potential energy, and potential energy can be looked at like chemical potential (which can be compared to gravitational potential) in this case we cannot describe the total internal energy only by the kinetic energy of the system.. That is to say - the temperatures and masses of the two systems being held constant under isothermal conditions doesn't really tell us much about the kinetic energy. Hopefully this was helpful, Cheers..
  22. Hello, Unfortunately 4-piperidone is a precursor to a controlled substance so I'm not willing to answer this question for you. I will give you a good place to get an answer though if you're working at a university lab or a company. Your lab should have a controlled substance drawer, and in that drawer will be information about how to use all of the controlled substances, typically a precursor to a controlled substance will also be in that drawer along with relevant documentation. Otherwise you can get plenty of procedures from Sci-Finder. Cheers
  23. Okay, well let's walk through it and see if we can get to an answer... I will give you some other hints... 1. "Chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. Breaking or making of chemical bonds involves energy, which may be either absorbed or evolved from a chemical system. Energy that can be released (or absorbed) because of a reaction between a set of chemical substances is equal to the difference between the energy content of the products and the reactants. This change in energy is called the change in internal energy of a chemical reaction." - http://en.wikipedia.org/wiki/Chemical_thermodynamics#Chemical_energy 2. "Molecules undergo many characteristic internal vibrations. Potential energy stored in these internal degrees of freedom contributes to a sample’s energy content, [9] [10] but not to its temperature. More internal degrees of freedom tend to increase a substance's specific heat capacity, so long as temperatures are high enough to overcome quantum effects." - http://en.wikipedia.org/wiki/Heat_capacity#Extensive_and_intensive_quantities 3. "The heat capacity of most systems is not a constant. Rather, it depends on the state variables of the thermodynamic system under study. In particular it is dependent on temperature itself, as well as on the pressure and the volume of the system." - http://en.wikipedia.org/wiki/Heat_capacity#Extensive_and_intensive_quantities Remember specific heat describes the substance, and specific heat describes the entire system. Remember: Increasing pressure on reactions that involves gasses will in crease the reaction rate. If you increase the pressure on solids or liquids it will have no effect on reaction rate. Also remember that, Chemical potential increase in areas of higher concentration and decreases in areas of lower concentration. That is to say: "Based upon this finding, we can conclude that the tendency μ of substances to change is not only dependent upon the types of those substances, but also upon their amounts n: The greater the amount of a substance (or the mass proportional to it) in the reaction chamber, the higher its expected potential μ should be. Closer scrutiny of this effect which is known as mass ac- tion shows that, in this case, the quantity n itself is unimportant. It is n in relation to the vol- ume V in which a substance is distributed, meaning its concentration c = n/V, that is impor- tant. If B or C, or both, participate as pure substances in a reaction, meaning at fixed concen- trations, their amounts nB and nC have no influence upon the state of equilibrium and there- fore, upon the amounts of BD and CD formed. How much or how little of a substance is pre- sent in this case, is apparently not decisive but rather how densely or loosely it is distributed in the space. This means that the more cumu- lative and concentrated the application, the more intense the effect. In other words, the mass of a substance is not decisive for mass action, but its “massing”, its “density“ in a space: not the amount, but the concentration. Cato Maximilian GULDBERG and Peter WAAGE of Norway brought our attention to this in the year 1864. Thus, the chemical potential of substances and the tendency to change increases according to how strongly concentrated they are. Conversely, the chemical potential goes down when the concentration of a substance decreases. We will use an example from everyday life to illus- trate this. According to the values of the chemical potentials, pure water vapour must con- dense at room conditions:" - http://docs.google.com/viewer?a=v&q=cache:4JHbuxVJWzgJ:www.job-stiftung.de/pdf/skripte/Physical_Chemistry/chapter_5.pdf%3FhashID%3D46fr9mvrkqcdaf0d1m9jdq0o90+chemical+potential+increases+with+concentration&hl=en&gl=za&pid=bl&srcid=ADGEESgn7cmu8rryQ0p1j1N71uXWQG7l3JIoFTCWK7rQ1ibhoSt1dOVBuiqWsbnQ72a61LFVv1tx259uYxmj1x2BbeTuU1k-BwoaDr3_Kcm-CKIF7WUGycbvzZ2l7llOastjpi5LI-G9&sig=AHIEtbQRsM4qshFH-HxI3FZArz6ef_lUNQ Please read the link above because it will better explain all of this not only mathematically but semantically as well. You can look at chemical potential like gravitational potential to see why it is not always the same in different concentrations - "the gravitational potential at a location is equal to the work (energy transferred) per unit mass that is done by the force of gravity as an object moves to that location from a reference location. It is analogous to the electric potential with mass playing the role of charge. By convention, the gravitational potential is defined as zero infinitely far away from any mass. As a result it is negative elsewhere." - http://en.wikipedia.org/wiki/Gravitational_potential "Potential Energy An object can store energy as the result of its position. For example, the heavy ball of a demolition machine is storing energy when it is held at an elevated position. This stored energy of position is referred to as potential energy. Similarly, a drawn bow is able to store energy as the result of its position. When assuming its usual position (i.e., when not drawn), there is no energy stored in the bow. Yet when its position is altered from its usual equilibrium position, the bow is able to store energy by virtue of its position. This stored energy of position is referred to as potential energy. Potential energy is the stored energy of position possessed by an object." - http://www.physicsclassroom.com/class/energy/u5l1b.cfm That is to say, though you've kept the mass and the temperature the same in each container, since their pressures are different, are the molecular configurations different or are they the same, what does the information about chemical potential and concentration provided in this post suggest? Hope this helps.. Cheers *note molecular configuration in this sense means position of molecules relative to each other. Not bond configuration.
  24. Hi Finter, you've confused the conditions. I stated that we are in isothermal conditions for the one container that has been compressed, as you wanted in your first question. This was to hold the temperatures between the two containers constant at constant mass. You can reverse the roles of the container but either way you will need an external heating or cooling source on one of them to hold the temps constant with constant mass. If you simply start compressing one of the containers more, you cannot answer you question about the total energy. The internal energy has two parts. Kinetic and potential - you have mistakenly stated that these two energies are the same. They are not. The kinetic energy is directly proportional to the temperature, but the internal energy is not. To understand the difference you need to look at the chemical potential. I have outlined how to do this in the previous post. Thus to answer your question.. are the energies the same for the two containers under the conditions that you described, or when you compress one even more and hold that container or the other uncompressed container at constant mass and temp via isothermal conditions... Well, if the temps are the same the kinetic energy is the same, but that says nothing about the internal energy since it is not proportional to the temperature and can be better explained by the specific heat.. Thus, to answer that question for yourself you will have to go through the exercise I gave you before. Your current association between specific heat and temperature will not answer your question. Swansont thought you were talking about the kinetic energies, I assure you he is not suggesting that the internal energy is also proportional to the temperature. this is from his own link: "Temperature is not directly proportional to internal energy since temperature measures only the kinetic energy part of the internal energy, so two objects with the same temperature do not in general have the same internal energy (see water-metal example). Temperatures are measured in one of the three standard temperature scales (Celsius, Kelvin, and Fahrenheit)." - http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper.html So, back to the thought experiment to help you prove this to yourself... If an equal amount of reactant is added to the two containers, which one will react faster? Why? What does that say about the internal energy (the chemical potential) of each container. Their temperatures and mass are the same due to isothermal conditions, but their pressures are not the same. *note the hints I gave you in the previous post as well as the mathematical relationships and the chemical potentials direct relationship to concentration. Cheers.
  25. Okay, my apologies, then I stand corrected about your position regarding the maths. Okay, well we can test this theory with a thought experiment. Absent of any external heating and cooling sources the larger container will be colder than the smaller container - meaning that their kinetic energies are not the same. (adiabatic conditions) In isothermal conditions, when we are holding temperature and mass constant.. then their kinetic energies are the same, because their temperatures are the same... Now, as for their internal energies, well that would depend on their specific heat. So, the question now is, if we are using isothermal conditions, and we want to check to see of the internal energies are the same, then we simply must take the two containers of let's say 1g of an identical gas in each.. but, remembering that both containers are under a different pressure, and raise or lower their temperature by 1 degree K. So the question is, which container will experience an increase in temperature faster, or will the increase in temperature be the same? Another question will be covered below.. The potential energy is not the same as the kinetic energy. When talking about molecules the potential energy is best described by the structural arrangement of the atoms in the molecules and with supramolecular structures as the arrangement of the molecules in the supramolecular structure. So now we must talk about the molecules and the chemical potential. A molecule has a higher chemical potential in areas of higher concentration and a lower chemical potential in areas of lower concentration. In thermo (when holding entropy and volume fixed) - the chemical potential is described as the amount the system's energy would increase if one additional particle was added to the system. At equilibrium chemical potentials are equal, and no energy is being released - i.e. - no energy is being converted to kinetic energy and increasing the temperature of the system. Mathematically speaking: a.) temperature, is the derivative of entropy with respect to energy. b.) chemical potential: In order to get equilibrium from two reactive systems we need the derivative of entropy with respect to the number of molecules. The ratio of the chemical potential over the temperature. c.) Pressure: In order to get equilibrium from two systems with differing volumes we use the derivative of entropy with respect to volume. Which can be viewed as the ratio of pressure over temperature. I will give you a hint to help with the thought experiment. Increasing the pressure on chemical reactions involving gasses increases the rate of the reaction, but increasing the pressure on reactions of solids and liquids does not. Q. In the case of your two containers the temperatures are the same, but the pressures are not. Thus if the conditions in the two containers are kept as described in your question and a reactive substrate is added to the gasses, the reaction of one container will go faster, but the question is, why and can this increase in rate be attributed to a higher internal energy - with respect to chemical potential - in one container over the other? *note remember what I said above about chemical potential and concentration. I think this is a good place to stop and check our bearings to see that they match up.. Cheers.. Another hint: "Internal energy has two major components, kinetic energy and potential energy. The kinetic energy is due to the motion of the system's particles (translations, rotations, vibrations), and the potential energy is associated with the static constituents of matter, static electric energy of atoms within molecules or crystals, and the static energy of chemical bonds. The internal energy of a system can be changed by heating the system or by doing work on it;[1] the first law of thermodynamics states that the increase in internal energy is equal to the total heat added and work done. If the system is isolated, its internal energy cannot change." - http://en.wikipedia.org/wiki/Internal_energy
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