ch 18: ketones and aldehydes

Question 1

ketones

Answer 1

carbon double bond to O
central carbon attached to 2 carbons

Question 2

aldehydes

Answer 2

carbon double bonded to O
central carbon attached to one carbon and H

Question 3

is the carbon double bounded to the O electrophilic or nucleophilic

Answer 3

electrophilic

Question 4

how is reactivity related to electron donating groups?

Answer 4

the more electron donating groups bonded to an C=O, the less reactive they are to nucleophiles

Question 5

are aldehydes or ketones more reactive to nucleophiles?

Answer 5

aldehydes

Question 6

acyclic aldehyde nomenclature

Answer 6

find the longest chain contain CHO group and change ending from -e to -al
- number the chain to make CHO = C1

Question 7

cyclic aldehyde nomenclature

Answer 7

name the ring and add -carbaldehyde
- do not number

Question 8

what can be used in place of numbers for aldehyde nomenclature?

Answer 8

greek letters
- alpha is the carbon next to aldehyde functional group
- beta is next to alpha, and so on

Question 9

acyclic ketone nomenclature

Answer 9

find the longest chain containing C=O and change ending from -e to -one
- number the chain to give C=O the lowest number

Question 10

cyclic ketone nomenclature

Answer 10

numbering begins at C=O but you do not need to include the number

Question 11

what acyl groups need to be named at substituents?

Answer 11

formyl, acetyl and benzoyl groups

Question 12

if another functional group has higher priority, what are the names of ketones and aldehydes?

Answer 12

ketone = oxo
aldehyde = formyl

Question 13

do ketones or aldehydes have higher priority in nomenclature?

Answer 13

aldehydes

Question 14

do ketones and aldehydes have high boiling points?

Answer 14

yes, higher than alkanes or ethers but lower than alcohol because they cannot hydrogen bond to each other

Question 15

are ketones and aldehydes good solvents?

Answer 15

yes for alcohol because lone pair onO can accept hydrogen bonds from O-H or N-H

Question 16

where do aldehydes and ketones show strong C=O peaks in IR spectra?

Answer 16

1700-1730

Question 17

where does the C-H bond of an aldehyde show a peak in IR spectra?

Answer 17

1-2 peaks at 2700-2830

Question 18

what leads to lower frequency for aldehydes or ketones?

Answer 18

conjugation leads to weaker C=O, so its lower frequency

Question 19

where does aldehyde C-H absorb on C NMR spectra

Answer 19

9-10ppm

Question 20

where does C=O absorb on NMR spectra

Answer 20

190-215

Question 21

a or b saturation effects on C=O absorption of C NMR spectra

Answer 21

190-200

Question 22

what is used to oxidize primary alcohols into aldehydes?

Answer 22

NaOCl/TEMPO
1. DMSO,COCL2 2. Et3N
PCC/CH2CL2

Question 23

what oxidizes secondary alcohols into ketones?

Answer 23

1. DMSO, COCL2 2. Et3N
   (swern oxidation)

Question 24

oxidative cleavage of alkenes

Answer 24

1. O3, ChCl2 2. Me2S

Question 25

hydration or hydroboration/oxidation of alkynes into ketone

Answer 25

1. H2SO4, Hg2+ 2. H2O

Question 26

hydration or hydroboration/oxidation of alkynes into aldehyde

Answer 26

hydration or hydroboration/oxidation of alkynes into ketone

Question 27

carboxylic acid reduction to primary alcohol to aldehyde

Answer 27

LiALH4 DIBAL-H or effective sources of H followed by H2O to reform C=O

Question 28

synthesis of ketones from nitriles

Answer 28

1. MeLi, Et2O 2. H3O+ 1. grignard reagent 2. H3O+

Question 29

synthesis of ketones from acid chlorides

Answer 29

1. 2Li 2. CuI

Question 30

general reactions of aldehydes and ketones

Answer 30

reaction at C=O with nucleophiles (addition)

Question 31

hydration of aldehydes and ketones

Answer 31

H2O in presence of an acid or base catalyst can add H and OH across the C=O to form a gem-diol

Question 32

what does hydration of ketone and aldehydes work well with?

Answer 32

only with unhindered aldehydes or aldehydes with nearby electron withdrawing groups

Question 33

what does increasing the number of R groups on the C=O do to the reactivity of the hydration reaction?

Answer 33

decreases the amount of hydrate at equilibrium because the electron withdrawing groups stabilize the C=O

Question 34

base catalyzed hydration

Answer 34

nucleophile attack by OH followed by protonation

Question 35

what does the reaction rate do under basic conditions?

Answer 35

increases because OH is a strong nucleophile

Question 36

acid catalyzed hydration

Answer 36

acid protonates the C=O and H2O backside attacks the carbocation H2O reacts again to deprotonate and form gem-diol

Question 37

nucleophilic addition of CN

Answer 37

treatment of aldehyde or ketone with NaCN and strong acid adds CN to carbon and OH on other side

Question 38

what can the CN group be hydrolyzed with?

Answer 38

carboxy group by heating an aqueous acid

Question 39

addition of amines to aldehydes/ketones

Answer 39

primary amine (RNH2) makes an imine (RRC=N-R) - schiff base

Question 40

hydration of imines

Answer 40

it can be converted back to C=O by hydrolysis and mild acid - exact reverse of the formation by using H3O+

Question 41

acetyl formation

Answer 41

react with 2 ROH to from acetals on top and bottom

Question 42

what happens when a diol is used in place of 2 ROH?

Answer 42

a cyclic acetal is formed

Question 43

mechanism for acetal formation

Answer 43

1. C=O gets protonated to OH and double bond breaks 2. ROH attacks carbocation 3. acid attacks H and lone pair goes to the OR 4. OH attacks H to make H2O 5. H2O leaves and forms carbocation 6. ROH attacks carbocation 7. acid attacks ROH and deprotonates to form acetal

Question 44

can an acetal reaction be reversed?

Answer 44

yes, it can be hydrolyzed back to an aldehyde or ketone by treatment with aqueous acid - using a large excess of H2O

Question 45

what are acetals used as?

Answer 45

protecting groups for aldehydes and ketones

Question 46

how are acetals used to protect the ketones and aldehydes?

Answer 46

by creating an acetal at the ketone to reduce the other product and then bring back the ketone/aldehyde 1. protection by acetal 2. reduction by LiAlH4 and H2O 3. deprotection by H2O, H+