Aldehydes and Ketones

Question 1

Carbonyl

Answer 1

double bond between a carbon and an oxygen

Question 2

Ketone

Answer 2

two alkyl groups bonded to a carbonyl carbon

Question 3

Aldehyde

Answer 3

one alkyl group and one hydrogen bonded to a carbonyl carbon

Question 4

Nomenclature Aldehyde

Answer 4

-e of alkane name is replaced by -al

methane -> methanal
ethane -> ethanal

Question 5

Common Names Aldehydes

Answer 5

Formaldehyde (methanal)
Acetalaldehyde (ethanal)
Propionaldehyde (propanal)
Butyraldehyde (butanal)
Valeraldehyde  (pentanal)

Question 6

If an aldehyde is attached to a ring, the suffixed _____ is used.

Answer 6

-carbaldehyde

cyclopentanecarbaldehyde

Question 7

Nomenclature Ketones

Answer 7

-e of alkane is replaced with -one

ketones as substituents are using oxo or keto prefixes

2-propanone 2 butanone

3-oxobutanoic acid

Question 8

Physical Properties of Aldehyde and Ketones

Answer 8

dipole of carbonyl is stronger than the dipole of alcohol due to double bond of oxygen being more electron withdrawing

this increases intermolecular attractions and increasing boiling point but less than alcohols due to lack of H bonding

act as electrophiles due to the negative charge on the oxygen

aldehydes are more reactive towards nucleophiles due to less sterics and fewer alkyl donating groups

Question 9

Forming Aldhydes

Answer 9

Primary Alcohol with PCC (parital oxidation)

too much oxidation leads to carboxylic acid!

Question 10

Forming Ketones

Answer 10

Secondary Alchol with Sodium/Potassium Dichromate salts or CrO3 or PCC

stops at ketone stage

Question 11

Nucelophilic Addition Reaction

Answer 11

adding of Nu to a carbonyl compound

carbonyl carbon is the electrophile

1) Nu forms covalent bond with carbonyl carbon breaking the pi bond
2) pi bond electrons go to the oxygen and its negative with extra electons
3) O- now accepts a proton (H) to form an alcohol

IF a leaving group is present, the carbonyl can reform as the leaving group leaves instead

Question 12

Hydration

Answer 12

in presense of water, aldehydes and ketones form geminal diols

1) waters oxygen attacks carbonyl carbon
2) O- takes the H from the bonded water resulting in two alcohol groups or a diol

proceeds slowly but rate increases with acid/base addition

Question 13

Hemiacetals/Hemiketals

Answer 13

like hydration but when one equivalent of alcohol is used

1) ROH oxygen attacks carbonyl carbon
2) O- takes H from alchol leading to OH and OR group

Question 14

Acetal/Ketal

Answer 14

like hemiacetal formation but two equivalents of alcohol are used (Sn1)

1) ROH oxygen attacks carbonyl carbon
2) O- takes H from alcohol and forms OH and OR group
3) OH gets protonated in acidic conditions and leaves as second equivalent attacks the formed carbocation

acetal made with aldehyde

ketal made with ketone

Question 15

Imines Formation

Answer 15

compound with nitrogen atom double bonded to a carbon attom

condensation reaction

1) NH3 attacks carbonyl carbon forming O-
2) O- gets protonated twiceand leaves as a water,
3) NH3 loses a hydrogen and uses lone pair to form double bond with carbonyl carbon with NH2
4) NH2 loses a hydrogen to form water and a stable NH

R-C- R

C= NH

Question 16

Nitrogen and nitrogen based functional groups are goood ____ because of the lone pair of electrons on the nitrogen can react with the _____ carbonyls of aldehydes and ketones

Answer 16

nucleophiles

electrophilic

Question 17

Enamine

Answer 17

tautomerized imines where a couble bond and a nitrogen group exist

Question 18

CyanoHydrins

Answer 18

hydrogen cyanide is a nucleophile with tripple bonds AND an electronegative nitrogen atom making it acidic

1) Hydrogen dissociates, making the cyanide anion nucleophilic and attack the carbonyl carbon
2) O- picks up an H forming an OH

occurs when HCN reacts with aldehyde/ketones

stability gained from new C-C bond

Question 19

Oxidation of Aldehydes

Answer 19

when further oxidized, they form carboxylic acids

potassium permanganate

chromium trioxide
silveroxide
hydrogen peroxide

Question 20

Reduction By Hydride Reagents

Answer 20

aldehydes and ketones can be reduced to alcohols with hydride reagents

LiALH4 and NaBH4