Answers to Concept Checks

6.1

The suffix  for an  aldehyde    is  –al.    The suffix  for a   ketone  is  –one.

The alkane  will    have    the lowest  boiling point,  followed    by  the aldehyde    and then    the alcohol.

The boiling point   of  the aldehyde    is  elevated    by  its dipole, but the boiling point   of  an  alcohol is

further elevated    by  hydrogen    bonding.

The carbon  in  a   carbonyl    is  electrophilic;  it  is  partially   positively  charged because oxygen  is

highly  electron-withdrawing.

Aldehydes   can be  formed  by  the oxidation   of  primary alcohols,   but can only    be  produced    using

weaker  (and    anhydrous)  oxidizing   agents  like    PCC—otherwise,  they    will    oxidize fully   to  carboxylic

acids.  Ketones can be  formed  by  the oxidation   of  secondary   alcohols.   Other   methods can be  used

as  well    (ozonolysis,    Friedel–Crafts  acylation), but these   are outside the scope   of  the MCAT.

6.2
With one equivalent of alcohol, aldehydes and ketones will form hemiacetals and hemiketals,
respectively. With two equivalents of alcohol, the reaction will run to completion, forming acetals
and ketals, respectively.
The reaction that occurs is a condensation reaction because a small molecule is lost, and also a
nucleophilic substitution reaction. This reaction results in the formation of an imine (or, for
nitrogen-containing derivatives: oximes, hydrazones, or semicarbazones).
When HCN reacts with an aldehyde or ketone, a cyanohydrin is produced, which is a stable
product.

6.3
Oxidizing an aldehyde yields a carboxylic acid. Common oxidizing agents include KMnO 4 , CrO 3 ,
Ag 2 O, and H 2 O 2.
Reducing an aldehyde or ketone yields an alcohol. Under certain conditions not tested on the
MCAT, aldehydes and ketones can be reduced all the way to alkanes. Common reducing agents
include LiAlH 4 and NaBH 4.