IB chemistry may 2019 boiling points

[Juliette]

Hi
the answer is B)
i really hesitated with D)

i agree the lowest BP is CH3CH2CH2CH3 because it is non polar
the second lowest BP is CH3COCH3 becasue it is polar

CH3CH(OH)CH3 is polar with H bonds and a molecular weight of 60
CH3CO2H is polar with H bonds and a molecular weight of 60

so how do we decide which has the higher boiling point??

[Aung_Htet_Thar]

Hi
Between CH3CH(OH)CH3 and CH3COOH or CH3CO2H, the former is alcohol and the latter is acid. And acid have smaller molecular structure than alcohol in addition to having hydrogen bonds. So, smaller molecular compounds are much more difficult to break which make them have high boiling point.