Pyruvic acid structure

Pyruvic acid structure.

Due to the presence of dipole-dipole interactions, aldehydes and ketones have higher boiling points than alkanes of similar size and structure. The carbonyl oxygen of aldehydes and ketones can undergo hydrogen bonding with water. High water solubility is especially true of lower molecular weight species such as formaldehyde and acetone.

Reactions of aldehydes and ketones are one of the largest and most important groups for the new MCAT. To help make their mechanisms more coherent and keep them organized, it helps to remember that most reactions of aldehydes and ketones belong to one of two classes, those involving nucleophilic attack on the carbonyl carbon and those involving electrophilic attack on the α carbon. (aldol condensation is in both groups). The reactions of aldehydes and ketones include, reduction, oxidation, hemiacetal & acetal formation, imine & enamine formation, cyanohydrin formation, keto-enol tautomerism and aldol addition.

The reactions above are crucial through-out biochemistry, which is why they are so important to the MCAT writers. For example, ring formation in glucose is an example of hemi-acetal formation. Formation of imine occurs in both of the key reactions of the non-oxidative phase of the pentose phosphate pathway, transaldolase and transketolase. Likewise, aldol addition occurs in the aldolase mechanism in glycolysis & gluconeogenesis.