Acidity of lactic acid and propanoic acid

[Michael_Light]

Homework Statement

i) Is lactic acid,CH₃CH(OH)COOH a stronger or weaker acid than propanoic acid (CH₃CH₂COOH)

ii) Another question is does ketone reacts with phosphorus pentachloride PCl₅?

Homework Equations

The Attempt at a Solution

(i) I guess lactic acid is a stronger acid because the oxygen atom on the hydroxyl group is very electronegative thus increases the polarity of the -OH bond on the carboxyl group, so H⁺ are more easily released. (Please correct me if i am wrong)

(ii) I can't find any relevant information from my textbook and even on google, but I encountered this type of question from my exercise book.. Can anyone guide me?

 

[Infinitum]

Hi Michael!

For (i) you are correct that lactic acid is stronger. -OH in an alkyl chain acts as electron withdrawing due to -I effect.

For (ii) you probably didn't google it well, as it is quite a standard reaction in organic chemistry.

Ketones react with phosphorus penta-chloride to give acid chlorides.

http://www.ch.ic.ac.uk/local/organic/tutorial/DB_Carbonylnotes1.pdf

 

[chemisttree]

...snip

Ketones react with phosphorus penta-chloride to give acid chlorides.

Close, but not quite. The product isn't called an acid chloride.

 

[Infinitum]

Close, but not quite. The product isn't called an acid chloride.

Whoops, I meant alkyl chlorides, specifically geminal.