Download L2 - Aldehydes and Ketones

Aldehydes and
Ketones
Carbonyl Compounds
• Contain
C=O double
bond.
• Include
many
classes of
compounds.
Aldehydes and Ketones
The carbonyl group:
Aldehydes have at least one hydrogen attached
to the carbonyl group.
Ketones have two carbons attached to the
carbonyl group.
Some
common
aldehydes
and ketones:
We will not
be learning
common
nomenclature;
you are only
responsible
for IUPAC.
Name the Following:
Naming Aldehydes
Find the longest carbon chain that contains
the aldehyde group.
Number from the carbonyl carbon; even in the
presence of multiple bond.
Change ending of the root alkane name by
dropping –e and adding –al.
All other branches and groups are named and
located using standard IUPAC system.
Example:
2.
:O:
3.
4.
O
5.
4-bromo-3-ethyl
hexanal
:O:
1.
O
OH
OH
:
:Br:
1
Name the Following:
Naming Ketones
3-bromo-2,5dimethyl-4heptanone
:O:
4.
3.
:
:O:
2.
1.
:Br:
OH
:O:
Find the longest chain that contains C=O.
Using the root alkane name, drop the –e
ending and change to –one.
Number the longest carbon chain so the C=O
group has the lowest number.
Name and number other substituents as
before.
Example:
:O:
5.
:
:Br:
Physical Properties
The carbonyl group is moderately polar,
but it doesn’t have any hydrogens
attached, so it cannot hydrogen bond
between molecules.
Physical Properties, cont.
Physical Properties, cont.
Because of the polarity of the C=O group,
these groups can interact, but the
attraction is not as
strong as hydrogen
bonding.
This makes the
boiling point of
aldehydes and
ketones higher than
alkanes, but lower
than alcohols.
A Comparison
The C=O group can hydrogen bond with
water molecules.
Make a table in your notes:
This makes low molecular weight
aldehydes and ketones water soluble
(they have small hydrophobic sections).
Organic molecules (alkane, haloalkane, alcohol, ether,
aldehyde and ketone) on one axis, and the 3 intermolecular
forces on the other axis. Then, fill in the table using X’s
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Important Aldehydes and Ketones
Methanal (A.K.A. Formaldehyde)
•Gas at room temperature
•Formalin – 37% aqueous solution
•Sterilizer
•Embalming fluid
•Formaldehyde is starting material for
plastics such as Formica and Bakelite.
Important Aldehydes and Ketones, cont.
2-propaonoe (A.K.A. Acetone)
Important organic solvent used in
such things as nail polish remover.
Miscible with water.
Important Aldehydes and Ketones, cont.
Progesterone and testosterone (female and
male sex hormones) are ketones.
Some aldehydes and ketones are very fragrant
and are used in flavorings.
Vanillin (vanilla)
Cinnamaldehyde (cinnamon)
Citral (citrus flavoring)
Camphor (medicinal odor)
Reaction Review:
Primary alcohol oxidation
•A primary alcohol can undergo a two
step reaction:
–In the first reaction, the alcohol loses two
hydrogen atoms to form a carbonyl group
on a terminal carbon by an oxidizing
agent (O), creating an aldehyde.
Samples
–In the second reaction, the newly formed
aldehyde can undergo further oxidation
when the remaining hydrogen one the
carbonyl carbon is substituted with a
hydroxyl forming a carboxyl group,
creating a carboxylic acid.
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Reaction Review, cont.
Secondary alcohol oxidation
•A secondary alcohol can only undergo
one oxidation
–the alcohol loses two hydrogen atoms to
form a carbonyl group on an intermediate
carbon, creating a ketone.
– What about a tertiary alcohol?
Oxidation States and Organic Reactions:
In each of these reactions, identify the atom that is
oxidized by assigning oxidation states.
Tollens’ Test
In the presence of aldehydes, Tollens’ reagent
[containing (Ag(NH3)2)+] produces a silver
coating on glass.
Tollens’ and Benedict’s Test
The ease with which aldehydes are
oxidized allows us to test for the
presence of aldehydes with Tollens’
reagent or Benedict’s reagent. In
general, ketones fail to react with these
reagents.
Benedict’s Test
In the presence of aldehydes, Benedict’s
reagent (containing CuSO4) produces a red
copper precipitate.
Benedict’s
reagent in
comparison
to 2 glucose
solutions
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Write the reaction of ethanal
with both Tollens’ and Benedict’s
reagent; Then, identify the atoms
being oxidized and those being
reduced.
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