Download Chapter 23 - Simpson County Schools

CHAPTER 23
Aldehydes & Ketones
23.1 STRUCTURES OF ALDEHYDES & KETONES

Both contain the carbonyl group (C=O)

Aldehyde, written linearly as CHO

Ketone written linearly as CO
23.2 NAMING ALDEHYDES & KETONES
IUPAC Naming of Aldehydes:
 Select the longest continuous chain of carbon
atoms that contains the aldehyde group.
 The carbons of the parent chain are numbered
starting with the aldehyde group.
 Form the parent aldehyde name by dropping the
–e from the corresponding alkane and adding the
suffix –al.
 Other groups attached to the parent chain are
named and numbered as previously done.


Aromatic aldehydes are named after the
corresponding carboxylic acid. Thus the name
benzaldehyde is from benzoic acid
IUPAC Naming of Ketones:
 Select the longest continuous chain of carbon
atoms that contains the ketone group.
 Form the parent name by dropping the –e from
the corresponding alkane name and adding the
suffix –one.
 If the chain is longer than four carbons, it is
numbered so that the carbonyl group has the
smallest possible number; this number is
prefixed to the parent name of the ketone.
 Other groups attached to the parent chain are
named and numbered as previously done.


Draw the structural formulas for:

4-methylhexanal

Butanedial

2-pentanone

4 methyl-3-hexanone:

Draw the structural formulas for:

4-methylhexanal

1, 4-Butanedial

2-pentanone

4 methyl-3-hexanone:
NAME THE FOLLOWING:
NAME THE FOLLOWING:
MORE NAMING:
MORE NAMING:
1-phenyl-1-butanone
5-methyl-3-hexanone
23.3 BONDING & PHYSICAL PROPETIES
Low MW aldehydes & ketones (<5 C) soluble in
both organic solvents & water.
 Higher MW aldehydes & ketones (>5C) soluble in
organic solvents, insoluble in water.


Boiling point comparison of aldehydes, ketones &
alcohols:

In general…if 4 or fewer C atoms: alcohols have
higher boiling points than ketones, ketones have
higher boiling points than aldehydes.
Rate the following molecules based on boiling
points from lowest to highest:
 2,2-dimethylpropane (MW 72 g/mol)
 1,2-propanediol (MW 76 g/mol)
 1-butanol (MW 74 g/mol)
 butanal (MW 72 g/mol)

23.4 CHEMICAL PROPERTIES OF
ALDEHYDES & KETONES
Reactions of Aldehydes and Ketones:
 Products of alcohol oxidation. See alcohol notes!
 Reduced to alcohols.

Aldehydes yield primary alcohols
 Ketones yield secondary alcohols.

Easily undergo addition due to double bond
(C=O)
 Aldehydes oxidize readily to carboxylic acids.
Ketones can’t be oxidized as readily.

PRODUCTS OF ALCOHOL OXIDATION.
SEE ALCOHOL NOTES!
ALDEHYDES OXIDIZE READILY TO
CARBOXYLIC ACIDS.
Ketones can’t be oxidized as readily.
 Tollens, Fehling, and Benedict solutions do not
give a positive test for ketones; therefore, they
are used to distinguish between ketones and
aldehydes…you will do this in lab!
 What are the IUPAC names for these
compounds?

ALDEHYDES OXIDIZE READILY TO
CARBOXYLIC ACIDS.
Ketones can’t be oxidized as readily.
 Tollens, Fehling, and Benedict solutions do not
give a positive test for ketones; therefore, they
are used to distinguish between ketones and
aldehydes…you will do this in lab!
 What are the IUPAC names for these
compounds?

Ethanal
ethanoic acid
NAME AND DRAW THE PRIMARY OXIDATION
PRODUCT FOR THE FOLLOWING REACTION:
NAME AND DRAW THE PRIMARY OXIDATION
PRODUCT FOR THE FOLLOWING REACTION:
Cyclohexanal
Cyclohexanoic acid
(or cyclohexanecarboxylic acid)
REDUCED TO ALCOHOLS

Aldehydes yield primary alcohols, whereas
ketones yield secondary alcohols.


In biochemistry, aldehyde/ketone reduction is
reversible!
Ketosis – a metabolic condition caused by
starvation or a low-carbohydrate/high protein
diet.
During ketosis, the liver produces low-molar-mass
ketones that are water-soluble and easily dissolve in
the bloodstream to be transported to tissues.
 At the same time, some of these ketones are reduced
in the liver and the alcohol product is released in to
the blood.

DRAW THE ALCOHOL THAT IS THE KETONE
REDUCTION PRODUCT. (NOTE 1O OR 2O)
DRAW THE ALCOHOL THAT IS THE KETONE
REDUCTION PRODUCT. (NOTE 1O OR 2O)
EASILY UNDERGO ADDITION WITH ALCOHOLS TO
FORM:
hemiacetals & hemiketals – compounds that
contain an alkoxy and a hydroxy group on the
same carbon, and
 acetals & ketals- compounds that contain 2
alkoxy groups on the same carbon.



Aldehydes react with alcohols to form
hemiacetals: (ketones react to form hemiketals)
Hemiacetals react with a second molecule of the
alcohol to give an acetal:


If the alcohol and carbonyl group are within the
same molecule, the result is the formation of a
cyclic hemiacetal (or hemiketal):
Extremely important to carbohydrate chemistry
due to nearly all carbohydrates are found as
ringed molecules because they form
intramolecular hemiacetals or hemiketals. The
acetal/ketal reaction provides the means by which
carbohydrates link together to form the wellknown carbohydrate polymers such as sucrose
(table sugar), lactose (milk sugar) and starch
THE FOLLOWING THREE SUGARS ARE
CYCLIC HEMIACETALS OR HEMIKETALS
Circle the hemiacetal or hemiketal carbon in each.
Can we determine which are the hemiacetals/hemiketals?
23.5 COMMON ALDEHYDES & KETONES
What other functional groups do you see?



Formaldehyde (methanal) – highly soluble,
poisonous, useful in manufacturer of polymers,
biological specimen preservative.
Acetaldehyde (ethanal) – produced by the liver
after alcohol consumption as part one of a 2-step
detoxifying process. Polymers of ethanal, such as
metaldehyde is poisonous to slugs & snails and
sold as an active ingredient in pesticides.
Acetone (propanone) & methyl ethyl ketone (2butanone) – widely used as solvents
HOMEWORK

Review Questions:


1, 4, 6-8, 11
Paired Exercises

2-22, 28 (even)