# Why is the melting point of lactic acid higher than pyruvic acid

I have a quick question about pyruvic acid and lactic acid, which I think I know the answer too but I'm unsure.

The melting point of lactic acid is said to be higher than that of pyruvic acid despite very similar molecular masses.

Is this because lactic acid has 2 $\ce{OH}$ groups, and pyruvate only has 1, thus there are twice as many hydrogen bonds between lactic acid molcules that must be broken for the substance to melt?

• Do you men boil or melt? – A.K. Jan 4 '17 at 21:01
• @A.K. I know it sounds weird, and it seems way more intuitive to ask about the boiling point, but that literally is what the question asks. – frostedcake Jan 5 '17 at 0:47

Is this because lactic acid has 2 $\ce{OH}$ groups, and pyruvate only has 1 […]?
You probably know the structures of both; they both include a $\ce{COOH}$ group which you apparantly counted as a hydroxy group. You should not do that; the carboxy group ($\ce{COOH}$) has different properties than a lone hydroxy group ($\ce{CR2OH}; \ce{R} \ne \ce{OX}$). The most obvious is the $\mathrm{p}K_\mathrm{a}$ value which differs by about $10$ logarithmic units.