Glycolic acid and Sodium Hydroxide reactionWatch
In a past paper I've just done, it gave the structural formula of glycolic acid as HOCH2COOH and it asked for the reaction between that and NaOH.
HOCH2COOH + 2NaOH --> NaOCH2COONa + 2H20
As I'm aware that NaOH can react with both alcohol groups and carboxylic acid groups, but the markscheme (which my school produced) has:
HOCH2COOH + NaOH --> HOCH2COONa + H20
Is mine wrong? Or are they both correct?
Alcohols have a fairly high pka value (compared to carboxyl groups) and are usually only partially deprotonated by hydroxide. But once you've deprotonated the carboxyl group in glycolic acid (most acidic group is always deprotonated first) the resulting negative charge makes the alcohol proton even less acidic so now it won't be deprotonated by hydroxide. You might find it easier to think that the negative hydroxide will find it more difficult to approach the already negative glycoate ion. So the mark scheme is in fact correct.
Ah, thanks for clearing that up; but I'm pretty sure that this isnt on our specification; how would I know that alcohols have a higher pka than carboxyl groups? Or anything like that? Is it basically saying that a base will react more "readily" with the carboxylic acid group than the alcohol, and hence the negative charge repels any further reaction?
And only seven years too late. Welcome to the site, by the way, but it is best to stick to replying to posts people have made recently, especially if you're after a "thank you".