[mike_302]

Hey all. Can't quite figure this out... The teach tells us that carboxyl groups only appear at the end of a chain, but our text book says otherwise. Fine --> I can take that up with her later, but the question seems too simple for me to pass up.. And maybe it'll help me understand something:

The question says to show the condensation reaction between methanoic acid and 2-butanol . From my knowledge, that means the carboxylic acid will attach to the alcohol on it's second carbon? Butyl-2-methanoate? Make any sense?

Thanks for the, quite possibly, dumb question... Our lesson on carboxylic acids and esters was quite short.

[azmanam]

Start here:

http://www.cem.msu.edu/~reusch/VirtTxtJml/crbacid1.htm#crbacd6c

the (2-butyl) chain is referred to as a sec-butyl group.

http://www.chemspider.com/Chemical-Structure.71381.html - go with the systematic name.

[mike_302]

To be honest, the first page was a little over my head, but if I read the second page right, then it appears I was right in my answer to the question. Thanks for the confirmation.

[azmanam]

no, your naming was a bit off.  if you break an ester into two parts - the part that came from the alcohol and the part that came from the acid - we name esters by first listing the alcohol part with -yl at the end (sec-butyl, or 1-methylpropyl) then in a second word, we name the part that came from the acid with -anoate at the end (methanoate).  Although methanoate and ethanoate are almost always called by their common names, formate and acetate respectively.  so the IUPAC name for this molecule would be sec-butyl formate (or sec-butyl methanoate).  The way you wrote it above seemed to imply you were starting with the butane chain and naming the methanoate as a substituent on the 2- position.

[mike_302]

See, I think this is what gets me: Previously (with alcohols and ethers and ketones... etc) we named the longest carbon chain as the parent chain and we put numbers on it to say there was something special going on at a certain carbon... then we use -yl endings on carbonyl group branches... Hear it seems to be the other way around --> The longest chain is getting the -yl ending, and the shortest chain is getting a special "parent chain" name of "anoate"...   

Am I right in saying that, in esters, it doesn't matter what hte longest carbon chain is really... It is the carboxyl chain that is the main part, and whatever chain is attached to it gets the -yl ending (Let's just assume that my defenition of a parent chain is that it doesn't have an -yl ending... for the sake of me remembering this stuff)

[azmanam]

Am I right in saying that, in esters, it doesn't matter what the longest carbon chain is really

Yes.

It is the carboxyl chain that is the main part

Don't think of it so much in terms of parent alkane.  Can you see which part came from an alcohol, and which part came from a carboxylic acid?  That's the best way to think about naming esters.  It is different from simple alcohols or halides.

The general formula for esters is R¹COOR².  To name, you start with the alkyl chain directly attached to an oxygen atom (R², the part that came from an alcohol).  It gets the -yl ending.  Then take the chain attached to the carbon bearing the C=O double bond. (R¹, the part that came from the acid).  It gets the -anoate ending.  Here are some examples:

http://en.wikipedia.org/wiki/Ethyl_acetate (a common solvent)
http://en.wikipedia.org/wiki/Isopentyl_acetate (smells like bananas)
http://www.chemspider.com/Chemical-Structure.11045.html (butyl propanoate)
http://www.chemspider.com/Chemical-Structure.7482.html (propyl butanoate)
http://www.chemspider.com/Search.aspx (cyclohexyl hexanoate)

[cliverlong]

Hey all. Can't quite figure this out... The teach tells us that carboxyl groups only appear at the end of a chain, but our text book says otherwise.  << snip >>

Draw a structural formula for the carboxyl group, COOH, showing all bonds and all atoms.

Count the "free" bond on the carbon atom.

Can the COOH group be bonded within a carbon chain or only at the end of a carbon chain?

Look up carbonyl group and its structural formula. From a carbonyl group's "free" bonds work out whether it can bond within a carbon chain or only at the end of a chain.


Clive