classicfan Posted October 27, 2009 Share Posted October 27, 2009 Hello, everyone! I am analyzing the molecule ethyl acrylate right now and having a little trouble because I've, unfourtunately, fallen behind in my organic chemistry course at the moment. I'm having a little trouble understanding this whole thing, so any help is appreaciated. Firstly, what sp3 chirality centres are there on the molecule? I don't really get this one, but is it the carbon double bonded to an oxygen an sp3 chiral carbon, with an R configuration? Are there any other chirality centres that I missed? Lastly, are any parts of the molecule conformationally mobile and what is the most stable conformation of ethyl acrylate? Unfourtunately, this part I'm really lost with and can't think of how to answer. Please, help me with this analysis. Thank you very much in advance! Link to comment Share on other sites More sharing options...
dr.syntax Posted October 27, 2009 Share Posted October 27, 2009 (edited) Hello, everyone! I am analyzing the molecule ethyl acrylate right now and having a little trouble because I've, unfourtunately, fallen behind in my organic chemistry course at the moment. I'm having a little trouble understanding this whole thing, so any help is appreaciated. Firstly, what sp3 chirality centres are there on the molecule? I don't really get this one, but is it the carbon double bonded to an oxygen an sp3 chiral carbon, with an R configuration? Are there any other chirality centres that I missed? Lastly, are any parts of the molecule conformationally mobile and what is the most stable conformation of ethyl acrylate? Unfourtunately, this part I'm really lost with and can't think of how to answer. Please, help me with this analysis. Thank you very much in advance! REPLY: It would be the CH2 double bonded Carbons to the CH . CHIRAL means handedness as in left hand, right hand. If the structure exhibits handedness it is chiral. If it does not it is called achiral. The C to O double bond exhibits no handedness. If you draw the complete structure including the hydrogens this becomes more apparent in the CH2 to CH double bonded carbons. Ref. ORGANIC CHEMISTRY By Harold Hart 8th edition. The C to O double bond has no chirality. ...Dr.Syntax Merged post follows: Consecutive posts mergedIt seems to me all the single bonded aspects of the molecule would be mobile. And the chirality centers would be the 2 carbons double bonded to each other in the CH2 to CH double bond. I think I am right about all this but am not 100% sure. From what I have told you try a google search as to chirality +ethyl acrylate and see what pops up. Wikipedia is usually pretty good about these sort of questions. ...Dr.Syntax.... As to the last question you asked:the answer would seem to me to be caused by,the result of, the high electronegative value of oxygen and it`s relation to the other atoms. It seems to me the different hydrogens would drawn toward the different oxygens and that if you can figure out what shape or formation would place the different hydrogens closest to the different oxygens you would have your answer as to what is the most stable conformation of this molecule. ...Dr.Syntax Edited October 27, 2009 by dr.syntax Consecutive posts merged. Link to comment Share on other sites More sharing options...
hermanntrude Posted October 27, 2009 Share Posted October 27, 2009 an sp3 carbon is one which has four single bonds. there only seems to be one to me and it's not the one dr syntax was talking about. whether it's chiral or not depends on whether the four things it's bonded to are different or not. Google chirality if you're stuck. for the second part I reccomend you do two things: 1) read up on conformers 2) make a molecular model. Use clay or blu-tak and sticks if necessary. Link to comment Share on other sites More sharing options...
dr.syntax Posted October 27, 2009 Share Posted October 27, 2009 an sp3 carbon is one which has four single bonds. there only seems to be one to me and it's not the one dr syntax was talking about. whether it's chiral or not depends on whether the four things it's bonded to are different or not. Google chirality if you're stuck. for the second part I reccomend you do two things: 1) read up on conformers 2) make a molecular model. Use clay or blu-tak and sticks if necessary. REPLY: You sounded like you know what the answer is so please tell her and me. You say it`s not the ones I mentioned. Please tell us just where this chiral is. Designate the atom or group. ... Dr.Syntax Link to comment Share on other sites More sharing options...
insane_alien Posted October 27, 2009 Share Posted October 27, 2009 this is homework help, we do NOT just give the answer away immediately. we try to help the user understand the problem so s/he can figure it out themselves. the whole give a man a fish and he'll eat for day, teach him to fish and he'll never go hungry again kind of thing. Link to comment Share on other sites More sharing options...
dr.syntax Posted October 27, 2009 Share Posted October 27, 2009 (edited) this is homework help, we do NOT just give the answer away immediately. we try to help the user understand the problem so s/he can figure it out themselves. the whole give a man a fish and he'll eat for day, teach him to fish and he'll never go hungry again kind of thing. I figured you would know so tell us all. I tried googling it and they are referencing me. What is the answer please. ...Dr.Syntax Merged post follows: Consecutive posts mergedREPLY: It would be the CH2 double bonded Carbons to the CH . CHIRAL means handedness as in left hand, right hand. If the structure exhibits handedness it is chiral. If it does not it is called achiral. The C to O double bond exhibits no handedness. If you draw the complete structure including the hydrogens this becomes more apparent in the CH2 to CH double bonded carbons. Ref. ORGANIC CHEMISTRY By Harold Hart 8th edition. The C to O double bond has no chirality. ...Dr.Syntax Merged post follows: Consecutive posts mergedIt seems to me all the single bonded aspects of the molecule would be mobile. And the chirality centers would be the 2 carbons double bonded to each other in the CH2 to CH double bond. I think I am right about all this but am not 100% sure. From what I have told you try a google search as to chirality +ethyl acrylate and see what pops up. Wikipedia is usually pretty good about these sort of questions. ...Dr.Syntax.... As to the last question you asked:the answer would seem to me to be caused by,the result of, the high electronegative value of oxygen and it`s relation to the other atoms. It seems to me the different hydrogens would drawn toward the different oxygens and that if you can figure out what shape or formation would place the different hydrogens closest to the different oxygens you would have your answer as to what is the most stable conformation of this molecule. ...Dr.Syntax I am getting some very different definitions depending on where I look. Dr.Syntax I`m going back to my original answer because I have more faith in Harold Hart than that dictionary. Edited October 27, 2009 by dr.syntax Consecutive posts merged. Link to comment Share on other sites More sharing options...
insane_alien Posted October 27, 2009 Share Posted October 27, 2009 that carbon is not chiral though. for it to stand a chance of being chiral you'd have to replace two of the hydrogens with something else at the very least. Link to comment Share on other sites More sharing options...
dr.syntax Posted October 27, 2009 Share Posted October 27, 2009 that carbon is not chiral though. for it to stand a chance of being chiral you'd have to replace two of the hydrogens with something else at the very least. and according to him chirality is all about handedness as in your left hand is the mirror image of your right hand.And nothing else. This book is the eighth edition so he`s evidently thought of as someone who knows the subject. I`ve got to get some sleep. ...Dr.Syntax 1 Link to comment Share on other sites More sharing options...
iNow Posted October 27, 2009 Share Posted October 27, 2009 Dr.S - I know you are sincerely trying to be helpful, and that is a laudable trait. However, especially here in the HW Help forum, it's important not to respond unless you have a clear enough understanding of the topic to teach it to others. Again, while I know you are seeking to be a good person and help others (and I commend that), your half answers based on stuff you googled are more likely to lead the questioner to be more confused. Let someone who is well versed on the topic respond, and then once the OP has been addressed and the questioner is satisfied, you can offer your own ideas and/or questions. I am not saying this to attack you. My intentions are kind. It's best not to contribute to HW Help threads unless you KNOW for CERTAIN how to approach the question and what the answer is. Take care. 1 Link to comment Share on other sites More sharing options...
insane_alien Posted October 27, 2009 Share Posted October 27, 2009 and according to him chirality is all about handedness as in your left hand is the mirror image of your right hand.And nothing else. This book is the eighth edition so he`s evidently thought of as someone who knows the subject. I`ve got to get some sleep. ...Dr.Syntax yes that is true, but for it to be chiral you need to have AT LEAST 4 different kinds of functional groups attached to the carbon. in this case you have the rest of the molecule and 3 hydrogens. its 4 seperate bonds but only 2 kinds. it is not chiral. i know your trying to help but two points on it, 1/ you are going about it the wrong way(giving out answers instead of teaching how to arrive at answers) 2/ you are trying to talk authoratatively on subjects where you do not have a firm grasp of the subject matter. the intentions are good, but the method is quite shaky. -1 Link to comment Share on other sites More sharing options...
classicfan Posted October 27, 2009 Author Share Posted October 27, 2009 there only seems to be one to me and it's not the one dr syntax was talking about. whether it's chiral or not depends on whether the four things it's bonded to are different or not. Were you talking about the CH3 on the right, the one single bonded to O? I also thought that it is the only one that exhibits an sp3 formation. And it's definitely not chiral, since it has three groups that are exactly alike (H's). One thing though, I've been researching and reading my book, but it's listed differently everywhere: can a chiral centre have a double bond? One website said that "If one of bonds is double or triple, the atoms to which it is attached are 'cloned'" (see here: http://www.ysbl.york.ac.uk/~garib/refmac/docs/theory/chiral.html) and it goes to break the double bond and add an extra carbon! I am baffled at that concept! Never heard it done, been trying to find similar situations, but cannot. Overall, as far as I realised, ethyl achrilate does not have any sp3 chirality centres. Link to comment Share on other sites More sharing options...
hermanntrude Posted October 27, 2009 Share Posted October 27, 2009 Were you talking about the CH3 on the right, the one single bonded to O? I also thought that it is the only one that exhibits an sp3 formation. And it's definitely not chiral, since it has three groups that are exactly alike (H's). One thing though, I've been researching and reading my book, but it's listed differently everywhere: can a chiral centre have a double bond? One website said that "If one of bonds is double or triple, the atoms to which it is attached are 'cloned'" (see here: http://www.ysbl.york.ac.uk/~garib/refmac/docs/theory/chiral.html) and it goes to break the double bond and add an extra carbon! I am baffled at that concept! Never heard it done, been trying to find similar situations, but cannot. Overall, as far as I realised, ethyl achrilate does not have any sp3 chirality centres. that's the conclusion I came to as well. It is sometimes possible for a compound to exhibit chirality without a distinct chiral centre. But the answer to the question "are there any sp3 chiral centres?" is no. Link to comment Share on other sites More sharing options...
dr.syntax Posted October 27, 2009 Share Posted October 27, 2009 (edited) Dr.S - I know you are sincerely trying to be helpful, and that is a laudable trait. However, especially here in the HW Help forum, it's important not to respond unless you have a clear enough understanding of the topic to teach it to others. Again, while I know you are seeking to be a good person and help others (and I commend that), your half answers based on stuff you googled are more likely to lead the questioner to be more confused. Let someone who is well versed on the topic respond, and then once the OP has been addressed and the questioner is satisfied, you can offer your own ideas and/or questions. I am not saying this to attack you. My intentions are kind. It's best not to contribute to HW Help threads unless you KNOW for CERTAIN how to approach the question and what the answer is. Take care. REPLY: That is good advise, and I take it in the spirit given.Sincerely,Dr.Syntax Merged post follows: Consecutive posts mergedyes that is true, but for it to be chiral you need to have AT LEAST 4 different kinds of functional groups attached to the carbon. in this case you have the rest of the molecule and 3 hydrogens. its 4 seperate bonds but only 2 kinds. it is not chiral. i know your trying to help but two points on it, 1/ you are going about it the wrong way(giving out answers instead of teaching how to arrive at answers) 2/ you are trying to talk authoratatively on subjects where you do not have a firm grasp of the subject matter. the intentions are good, but the method is quite shaky. I need to begin by stating that it is because Insane_Alien straightened me out about all this, that I do not have it completely backwards. Professor Hart was clear enough about all this, yet, I managed to get it completely backwards. What can I say. I am sorry for all confusion I caused. ...Dr.Syntax REPLY: The definition I am getting from both Harold Hart and ONE of the online Chemistry dictionaries is that it is all about handedness. That the word itself is derived from chier, Greek for hand. I am not set up to spell it using Greek letters. So the first question is: Is this molecule chiral or achiral . It appears to me that it is achiral. It`s mirror image is identical to it`s non-mirror image. I just now used a mirror to this test on the representation of the molecule and the mirror image is identical to the non-mirrored image. Anyone out there can do this simple test to prove or disprove what I just stated. So the molecule itself is achiral because it`s mirror image is the same as it`s non-mirrored image. Next : what determines a chiral center ? Quoting Harold Hart: " A carbon atom with four different groups attached to it is called an asymmetric carbon atom. This type of carbon atom is also called chiral center because it gives rise to stereoisomers,that is, it is stereogenic." unquote . SO MY ANSWER IS: It IS AN ACHIRAL molecule that has NO chiral centers. And I believe this to be the correct answer. As I stated earlier my reference is Harold Hart`s " Organic Chemistry: a short course, eighth edition ". My regards to all who took part in this discussion. Sincerely, ...Dr.Syntax ....I am very grateful to Insane_Alien for setting me straightening me out about all this. ...Dr.Syntax Edited October 28, 2009 by dr.syntax Consecutive posts merged. 1 Link to comment Share on other sites More sharing options...
hermanntrude Posted October 28, 2009 Share Posted October 28, 2009 REPLY: That is good advise, and I take it in the spirit given.Sincerely,Dr.Syntax Merged post follows: Consecutive posts merged REPLY: The definition I am getting from both Harold Hart and ONE of the online Chemistry dictionaries is that it is all about handedness. That the word itself is derived from chier, Greek for hand. I am not set up to spell it using Greek letters. So the first question is: Is this molecule chiral or achiral . It appears to me that it is chiral. It`s mirror image is identical to it`s non-mirror image. I just now used a mirror to this test on the representation of the molecule and the mirror image is identical to the non-mirrored image. Anyone out there can do this simple test to prove or disprove what I just stated. So the molecule itself is chiral. Next : what determines a chiral center ? Quoting Harold Hart: " A carbon atom with four different groups attached to it is called an asymmetric carbon atom. This type of carbon atom is also called chiral center because it gives rise to stereoisomers,that is, it is stereogenic." unquote . SO MY ANSWER IS: It IS a chiral molecule that has NO chiral centers. There is nothing about the definition of a chiral molecule that says there need be chiral centers. And I believe this to be the correct answer. As I stated earlier my reference is Harold Hart`s " Organic Chemistry: a short course, eighth edition ". My ragards to all who took part in this discussion. Sincerely, ...Dr.Syntax you're still getting it wrong, dr S. Chirality IS all about "handedness" but a molecule is chiral when it's mirror image is non-superimposable onto the original. In other words, if the molecule is symmetrical or flexible, it probably won't be chiral. While it is possible for a molecule to be chiral without having an sp3 carbon chiral centre, there are two reasons we don't need to worry about that: 1) the question asked us whether there were any sp3 chiral carbons, NOT whether the molecule was chiral 2) I may be wrong here but I suspect the molecule isn't chiral anyway. Link to comment Share on other sites More sharing options...
insane_alien Posted October 28, 2009 Share Posted October 28, 2009 it isn't chiral at all as the mirror image is the same as a rotation of the molecule. if it were chiral then the mirror image would not be the same as a rotation. lets use the hand example, your hands are the same but mirrored, if you rotate your left hand so the thumbs are the same way you can see they are not the same(they are chiral) if you rotate your left hand and it looked exactly the same as your right then they would not be chiral. do you understand now? Link to comment Share on other sites More sharing options...
hermanntrude Posted October 28, 2009 Share Posted October 28, 2009 a few hours with a molecular modelling kit can really help with this stuff Link to comment Share on other sites More sharing options...
dr.syntax Posted October 28, 2009 Share Posted October 28, 2009 a few hours with a molecular modelling kit can really help with this stuff Hello hermanntrude , I intend to get one soon. I can see how crucial such a kit if one desires to understand many aspects of chemistry. I bet they are fun to work with also. Regards, ...Dr.Syntax Link to comment Share on other sites More sharing options...
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