Reaction with amine

[ecoli]

We're doing figuring out an unknown experiment in my organic chem lab.

 

We're given a list of potential chemicals, and I was sure I narrowed it down.

 

The IR spec showed an amino group, and it is soluble in water, which means its a low molecular weight. The boiling point was 63 degrees... litmus test showed it was basic.

 

On the given list, 2-Butylamine is shown to have a boiling point of 63. So, I was pretty sure it was that.

 

The last test I did was to react it with phenyl isothiocyanate (in a one to one ratio) to create a phenylthiourea derivative. The solution turned green and became very hot. A sticky precipitate formed. I washed it with ligroin and a 1:1 ethanol-water solution (separately, of course). Then I dissolved it in hot ethanol, did a hot filtration. I cooled it down to let the crystals precipitate. Then a vacuum filtration to isolate the crystals.

 

According to my lab manual the melting point of the phenylthiourea ought to be 101 C... but the melting point I recorded was much lower, at 65 degrees celsius.

 

Is it possible that residual water in the crystals could significantly lower the melting point? I repeated this several times, nearly exactly to protocol and I'm still getting the same thing.

 

According to my book, none of the other Phenylthiourea derivatives we could make (assuming the unknown is something other then 2-Butylamine) are as low as 65 degrees.

 

There's another Benzamide test that I can do (although it's optional). I was wondering if I could have made a mistake in the experiment... or perhaps my lab manual is wrong? (though I doubt this).

[ecoli]

bumpity bump

[ecoli]

turns out my crystals weren't dry enough to get an accurate melting point reading. I figured it out now. Thanks.