Docsity
Log inSign up
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search Store documents

The best documents sold by students who completed their studies

Search through all study resources
Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

University Rankings

Discover the best universities in your country according to Docsity users

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

From our blog

Exams and Study
Go to the blog

Aldehydes and Ketones: Nucleophilic Addition to the Carbonyl ..., Study notes of Organic Chemistry

University of Central Lancashire (UCLan)Organic Chemistry

Carbonyl carbons are electrophilic sites and can be attacked by nucleophiles. The carbonyl oxygen is a basic site. Acetals are geminal diethers - structurally ...

Typology: Study notes

2021/2022

Uploaded on 09/27/2022

sctsh3
sctsh3 🇬🇧

4.8

(6)

296 documents

1 / 15

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
115
Chapter 17: Aldehydes and Ketones: Nucleophilic Addition
to the Carbonyl Group
17.1: Nomenclature (please read)
suffix: –al for aldehydes
–one for ketone
17.2: Structure and Bonding: The Carbonyl Group: Carbonyl
groups have a significant dipole moment
C
O
δ +
δ -
Aldehyde 2.72 D
Ketone 2.88
Carboxylic acid 1.74
Acid chloride 2.72
Ester 1.72
Amide 3.76
Nitrile 3.90
Water 1.85
C
O
C
O
Carbonyl carbons are electrophilic sites and can be attacked
by nucleophiles. The carbonyl oxygen is a basic site.
116
17.3: Physical Properties (please read)
17.4: Sources of Aldehydes and Ketones (Table 17.1, p. 693)
1. Oxidation of Alcohols
a. Oxidation of 1° and 2° alcohols (Chapter 15.9)
b. From carboxylic acids and esters (Chapter 15.3)
c. Ketones from aldehydes
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff

Partial preview of the text

Download Aldehydes and Ketones: Nucleophilic Addition to the Carbonyl ... and more Study notes Organic Chemistry in PDF only on Docsity!

Chapter 17: Aldehydes and Ketones: Nucleophilic Addition

to the Carbonyl Group

17.1: Nomenclature (please read)

suffix: –al for aldehydes

–one for ketone

17.2: Structure and Bonding: The Carbonyl Group: Carbonyl

groups have a significant dipole moment

C

O

Aldehyde 2.72 D

Ketone 2.

Carboxylic acid 1.

Acid chloride 2.

Ester 1.

Amide 3.

Nitrile 3.

Water 1.

C

O

C

O

Carbonyl carbons are electrophilic sites and can be attacked

by nucleophiles. The carbonyl oxygen is a basic site.

17.3: Physical Properties (please read)

17.4: Sources of Aldehydes and Ketones (Table 17.1, p. 693)

1. Oxidation of Alcohols

a. Oxidation of 1° and 2° alcohols (Chapter 15.9)

b. From carboxylic acids and esters (Chapter 15.3)

c. Ketones from aldehydes

2. Ozonolysis of alkenes (Chapter 6.12)

3. Hydration of alkynes (Chapter 9.12)

4. Friedel-Crafts Acylation – aryl ketones (Chapter 12.7)

17.5: Reactions of Aldehydes and Ketones: A Review and a Preview

Reactions of aldehydes and ketones (Table 17.2, p. 695)- Review:

1. Reduction to hydrocarbons (Chapter 12.8)

a. Clemmenson reduction (Zn-Hg, HCl)

b. Wolff-Kishner (H

NNH

, KOH, Δ)

Acid-catalyzed mechanism (p. 700):

protonated carbonyl is a better electrophile

Does adding acid or base change the amount of hydrate?

Does a catalysts affect ΔG

o

, ΔG

, both, or neither?

The hydration reaction is reversible

17.7: Cyanohydrin Formation

Addition of H-CN to the aldehydes and unhindered ketones.

(related to the hydration reaction)

The equilibrium favors cyanohydrin formation

Mechanism of cyanohydrin formation (p. 701)

17.8: Reaction with Alcohols: Acetals and Ketals

Acetals are geminal diethers - structurally related to hydrates,

which are geminal diols.

R R

C

O

OH

C

O H

R

R

+ H

2

O

- H

2

O

hydrate

(gem-diol)

aldehyde hemi-acetal acetal

(gem-diether)

ketone hemi-ketal ketal

(gem-diether)

R H

C

O

OR'

C

O H

R

H

+ R'OH

- R'OH

+ R'OH

- R'OH

OR'

C

OR'

R

H

+ H

O

R R

C

O

OR'

C

O H

R

R

+ R'OH

- R'OH

+ R'OH

- R'OH

OR'

C

OR'

R

R

+ H

O

Mechanism of acetal (ketal) formation is acid-catalyzed (p. 705)

The mechanism for acetal/ketal formation is reversible.

How is the direction of the reaction controlled?

Dean-Stark

Trap

O

a) NaNH 2

b) H

3

C-I

O

CH

3

The reaction cannot be done directly, as shown. Why?

Aldehyde

or ketone

hemi-acetal

or hemi-ketal

acetal

or ketal

17.10: Reaction with Primary Amines: Imines (Schiff base)

Aldehyde

or ketone carbinolamine Imine

O

C

R R

  • R'OH
  • R'OH

OH

C

OR'

R

R

  • R'OH
  • R'OH

OR'

C

OR'

R

R

  • H 2

O

  • H 2

O

OR'

C

R R

O

C

R R

  • R'NH

2

  • R'NH

2

OH

C

NHR'

R

R

  • R'NH 2
  • R'NH

2

NHR'

C

NHR'

R

R

  • H 2

O

  • H

2

O

N

C

R R

R'

Mechanism of imine formation (p. 709):

See Table 17.4 (p. 712) for the related carbonyl derivative,

oximes, hydrazone and semicarbazones (please read)

O

N

N-C 6

H 5

H 2

NOH

N

OH

phenylhydrazone oxime

C 6

H 2

NHNH 2

N

H 2

NHNCONH 2

N

H

NH

2

O

semicarbazide semicarbazone"

17.11: Reaction with Secondary Amines: Enamines

R R

C

O

NHR'

C

O H

R

R

  • H 2

O

R R

C

N

R'

R'NH 2

1° amine:

2° amine:

Imine

Iminium ion

R R

C

O

N

C

O H

R

R

R'

N

H

R'

R'

R'

R R

C

N

R' R'

  • HO

_

iminium ion enamine

ketone with

α -protons

Mechanism of enamine formation (p. 713)

R

C

O

N

C

O H

R

- HO

R'

N

H

R'

R'

R'

R

C

N

R' R'

R

H H R

H

H

R

H H

R

C

N

R' R'

R

H

_

- H

17.12: The Wittig Reaction

1979 Nobel Prize in Chemistry: Georg Wittig (Wittig Reaction) and H.C. Brown (Hydroboration)

The synthesis of an alkene from the reaction of an aldehyde

or ketone and a phosphorus ylide (Wittig reagent), a dipolar

intermediate with formal opposite charges on adjacent atoms

(overall charge neutral).

R

1

C

R

2

O

R

4

Ph C

3

P

R

3

R

3

C C

R

2

R

1

R

4

+ Ph

3

P=O

aldehyde

or ketone

triphenylphosphonium

ylide (Wittig reagent)

alkene triphenylphosphine

oxide

Accepted mechanism (p. 716)

• There will be two possible Wittig routes to an alkene.

• Analyze the structure retrosynthetically , i.e., work the synthesis

out backwards.

• Disconnect (break the bond of the target that can be formed by

a known reaction) the doubly bonded carbons. One becomes

the aldehyde or ketone, the other the ylide.

R 3

C C

R

2

R

1

R 4

Disconnect

this bond

C

R 2

R 1

O

R 3

C

R 4

Ph

3

P

C

R 2

R 1

PPh

3

R

3

C

R

4

O

- OR -

C C

CH 3

CH 2

CH 2

H

CH

3

CH

2

CH

3

17.13: Stereoselective Addition to Carbonyl Groups

(please read)

17.14: Oxidation of Aldehydes

Increasing oxidation state

C C

C C

C C

C OH C O

C

O

OR

CO

2

C NH

2 C NH C N

C Cl C Cl

Cl

C Cl

Cl

Cl

C Cl

Cl

Cl

Cl

RCH

2

- OH

R H

O

R H

HO OH

R OH

O

hydration

H

3

O

acetone

H

2

Cr 2

O

7

1 ° alcohol

H

3

O

,

acetone

H

2

Cr

2

O

7

H

2

O

CH

2

Cl

2

PCC

OH

CO 2

H CHO

1 ° alcohol

H

3

O

acetone

H

2

Cr

2

O

7

Carboxylic Acid Aldehyde

Aldehydes are oxidized by Cr(VI) reagents to carboxylic acids

in aqueous acid. The reactions proceeds through the hydrate

See Chapter 15.

Baeyer-Villiger Oxidation of Ketones. Oxidation of ketones

with a peroxy acid to give as esters (p. 732)

R R'

O

O

O

Cl

O H

R O

O

R'

ester

OH

O

Cl

Oxygen insertion occurs between the carbonyl carbon and

the more substituted α-carbon

CH 3

O

H 3

C

O

mCPBA

mCPBA

O

O

O

O

H C

H NMR Spectra of Aldehydes and Ketones: The

H chemical shift

range for the aldehyde proton is δ 9-10 ppm

The aldehyde proton will couple to the protons on the α-carbon

with a typical coupling constant of J ≈ 2 Hz

A carbonyl will slightly deshield the protons on the α-carbon;

typical chemical shift range is δ 2.0 - 2.5 ppm

δ = 9.8, t,

J = 1.8, 1H

δ = 1.65, sextet,

J = 7.0, 2H

δ = 2.4, dt,

J = 1.8, 7.0, 2H

δ = 1.65, t,

J = 7.0, 3H

δ= 2.5 (2H, q, J = 7.3)

2.1 (3H, s)

1.1 (3H, t, J = 7.3)

H

C H

C C CH

O

δ 7.0 -6.0 δ 2.7 - 1.

δ= 6.8 (1H, dq, J = 15, 7.0)

6.1 (1H, d, J = 15)

2.6 (2H, q, J = 7.4)

1.9 (3H, d, J = 7.0 )

1.1 (3H, t, J = 7.4)

C

C

CH

2

CH

3

C

O

H

3

C

H

H

C NMR:

The intensity of the carbonyl resonance in the

C spectrum

usually weak and sometimes not observed.

The chemical shift range is diagnostic for the type of carbonyl

ketones & aldehydes: δ = ~ 190 - 220 ppm

carboxylic acids, esters, δ = ~ 165 - 185 ppm

and amides

CDCl 3

O

carbonyl

carbonyl

O

H C 3

CH 2

CH 2

C OCH 2

CH 3

C

9

H

10

O

2

1H

s

2H

d, J = 8.

2H

d, J = 8.

2H

q, J= 7.

3H

(t, J= 7.5)

IR: 1695 cm

13

C NMR: 191

2H

2H

(q, J = 7.3)

5H

C

10

H

12

O

IR: 1710 cm

13

C NMR: 207

3H

(t, J= 7.3)