Friday, May 3, 2013
ACS question from study guide:
I have been working my way through the study guide and have found it to be a really good guide. I have a question about a practice question in the "nucleophilic substitution at carbonyl groups" section. It is question #18 that has to do with polymerization and im having trouble understanding the mechanism exactly. Thanks for any responses, and good luck Monday everyone.
Subscribe to:
Post Comments (Atom)
I'll take the case! Hold on :)
ReplyDeleteI missed this one too, so don't feel too bad :P Ooo oo! This question is about Nylon 6! We did a very similar reaction in lab (if you are taking lab this semester.) A condensation reaction is when two molecules form a new bond while removing a small molecule like water. On page 1195 of our book it says that step growth polymers like Nylon are sometimes also called condensation polymers, because they will lose a small molecule like water. So basically we need to make this reaction a dehydration.
ReplyDeleteSo if you look at the top of page 1197 in our book you can see the reaction with a ring (epsilon-caprolactam) forming the wanted polymer. The mechanism is not shown, but it does say that the base (OH-) will open up the ring. So we should be left with the straight chain... NH2-CH2-CH2-CH2-CH2-CH2-COOH. Now the nitrogen from one of those chains will attack the carbonyl carbon at COOH of another chain. Do you see how it would work?
I wish I could post pictures in the comments! Reply if you would like me to write it up in chemdraw and post it separately.
I forgot to mention, when the nitrogen attacks the next carbonyl carbon, water is removed, which makes part of this reaction a dehydration. This meets the qualifications for a condensation reaction which makes choice A the right answer.
ReplyDeleteOk makes sense, thanks!
ReplyDelete