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Aldehydes Aldehydes && KetonesKetones contain the carbonyl group, C=O.

R-C-H R-C-R’

or RCHO or R-CO-R’

O O

Aldehyde Ketone

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Both aldehydes and ketones contain the carbonyl group, C=O.

The H-C=O group of an aldehyde is called the formyl group.

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Aldehyde Nomenclature1. Find longest Carbon chain that

includes C of C=O.

2. Ending for name is “al” : alkane + al --> alkanal

3. Number chain to give C of C=O locant #1.

4. Aldehyde & ketone more important than alcohol group.

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Example of Naming Aldehydes

HO-CH2-CH2CH2CH-CH2CH2-CH

O

CH3

7-hydroxy-4-methylheptanal

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Ketone Nomenclature

1. Find longest Carbon chain that includes C of C=O.

2. Ending for name is “one” : alkane + one --> alkanone

3. Number chain to give C of C=O the lower possible locant.

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Example

CH3CH2CHCH2CCH2CH3

O

5-phenyl-3-heptanone

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Aldehyde & Ketone Bonding

* Carbon has 120° bond angles

* molecular shape around C is trigonal planar

O=C

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The C=O bond is polar covalent, has permanent dipole because of electronegativity difference between C and O....

C O–+

••••

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Aldehyde & Ketone Reactions

1. Oxidation

2. Reduction

3. Addition

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Oxidation means carbon forms more bonds to oxygen.

Aldehydes are easilyeasily oxidized to carboxylic acids:

R-C-H R-C-O-H

O O[O]

.

[O] means add oxygen from [O] means add oxygen from another source, like Oanother source, like O22..

1111

Ketones are NOT easily oxidized.

Reagents which oxidize aldehydes do NOT oxidize ketones.

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Reduction means forming more C-H bonds or decreasing the number of C-O bonds.

R-C-H R-CH-HH

O OHH[H]

aldehyde ---> primary alcoholaldehyde ---> primary alcohol

[H] means add H from another source

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R-C-R’ R-C-R’

O OHH

HH

[H]

ketone ---> secondary alcoholketone ---> secondary alcohol

Ketone Reduction

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Practice Problem

Draw the structure of the product of this reaction:

O

CH3CH2CCH2CH2CH3

[H]???

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Ketones are reduced to alcohols.

So: what is the alcohol related to the ketone shown?

CH3CH2CCH2CH2CH3

OH

H

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Addition Reactions of Aldehydes & Ketones

C=O++

––

electron pair donor (nucleophile) reacts at C

•• •• e– pair acceptor

(electrophile, often H+) reacts at O

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Alcohols add to the C=O of aldehdyes and ketones

RORO-HH symbol for alcohol ••

••

Electrophile at H

Nucleophile at O because electron pair donor

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General Reaction for ROH addition happens in 2 steps…

R-C-H + RORO-HH

OH+ (catalyst)

R-C-H

OROR

O-HH

hemi-acetal hemi-acetal

(product of first step)

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General Reaction for ROH addition, 2nd step is

R-C-H R-C-H + H2O

OROR OROR

O-HH OROR

hemi-acetalhemi-acetal acetalacetal

ROROH, H+

2nd step

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Example:

What hemi-acetal is formed in the reaction

CH3CH2C-H + CH3OH

O???

Hint:

RO of alcohol bonds to C of C=O,

H bonds to O of C=O

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CH3CH2C-H

OCH3

OH

CH3CH2C-H + CH3OH

OSo, the answer is:

Hemi-acetal

2222

Notes:• ordinarily, hemi-acetals are ordinarily, hemi-acetals are not not stable enough to stable enough to isolate from isolate from reaction.reaction.

• product usually obtained is product usually obtained is acetal.acetal.

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Formation of acetals is Formation of acetals is reversiblereversible: they can be decomposed simply by reversing the steps which led to their formation.

Formation uses excess ROH.Formation uses excess ROH.

Decomposition or hydrolysis Decomposition or hydrolysis uses excess Huses excess H22O.O.

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Example of Hydrolysis of Acetals:

C HOCH3

OCH3 H2O, H+

C-H + 2 CH3OH

O

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Ketones make hemi-acetals and acetals as well.

Predict structure of the acetal from the unbalanced reaction below:

CCH2CH3 + CH3OH

OH+

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CCH2CH3

OCH3

OCH3

Here ya go!