Ketones & Aldehydes

Question 1

Carbonyl group

Answer 1

sp2 hybridized C connected to an O by a double bond

Question 2

Carbonyl Group Reactions

Answer 2

• Nucleophilic attack at the carbonyl carbon
• The product of this attack can undergo 3 different types of reactions

Question 3

Nucleophilic Addition

Answer 3

C=O NaBH4/LiALH4, Grignard reaction

Question 4

Nucleophilic Substitution

Answer 4

• R1 good leaving group to C=O

Question 5

Nucleophilic Substitution + Replacement of O

Answer 5

If Nucleophile has lone pair- loses OH

Question 6

Ketone

Answer 6

Two alkyl or aryl groups bonded to the carbonyl carbon atom

Question 7

Aldehyde

Answer 7

• One alkyl or aryl group and one H bonded to the carbonyl carbon
  atom

Question 8

electrophile in Lewis acid

Answer 8

• Positively polarised carbon
• Bonding electrons are not shared
  equally

Question 9

electrophile in Lewis acid

Answer 9

• Positively polarised carbon
• Bonding electrons are not shared
  equally

Question 10

Nucleophile (Lewis base)

Answer 10

• Negatively polarised oxygen
• Bonding electrons are not shared
  equally

Question 11

Synthesis of ketones using organolithium reagents with carboxylic acids

Answer 11

• Carboxylic acid + organolithium reagent
• Dianion then to ketone

Question 12

Synthesis of ketones using organocuprates with acid chlorides

Answer 12

• Acid chloride add organocuprate (R2CuLi) then to ketone

Question 13

Synthesis of ketones from
nitriles

Answer 13

• Nitrile then add R1-Mg-X
• Mg salt of imine then add H3O
• C-N triple bond is polarised. Nucleophiles can add to CN by attacking the electrophilic carbon atom
  An imine

Question 14

Aldehyde synthesis by reduction of
nitriles

Answer 14

• Aluminium complex with reagent

Question 15

Aldehyde synthesis by reduction of acid chlorides

Answer 15

• Replacing halogen with Hydrogen

Question 16

Aldehyde synthesis by reduction of
esters

Answer 16

• Replace OR1 functional group with hydrogen

Question 17

Reactions of Ketones and Aldehydes

Answer 17

• Most common reaction is nucleophilic
  additionAddition of a nucleophile and a proton (H) across the C=O

Question 18

Basic Conditions with strong nucleophile

Answer 18

• A strong nucleophile adds to the carbonyl group to form an alkoxide
• A weak acid protonates the alkoxide to give the addition product
• Deprotonation, followed by loss of the
  nucleophile

Question 19

Acid Conditions with weak nucleophile and activated carbonyl

Answer 19

• Protonation activates the carbonyl group toward nucleophilic attack
• A weak nucleophile adds to the activated (protonated) carbonyl group
• Reverse reaction loss of the weak nucleophile, followed by deprotonation

Question 20

In acid addition of weak nucleophile

Answer 20

• Formation of a hydrate geminal diol
• Transfer of electrons break double bond protonation

Question 21

What state does ketone prefer

Answer 21

• Favours the non hydrated keto form

Question 22

What state does alderhyde prefer

Answer 22

• More likely to form stable hydrates
• Formalderhyde most reactive

Question 23

Reduction of Carbonyl

Answer 23

• Addition of sodium borohydride reduces ketone and alderhyde to alcohol

Question 24

Formation of imines

Answer 24

• Acid-catalysed addition of the amine to the carbonyl group
• Acid-catalysed dehydration
• Substituted imine is also called a Schiff base
  Condensation Reaction

Question 25

Condensations with hydroxylamine and hydrazine

Answer 25

• Hydroxylamine to oxime

Question 26

Enols and Enolates

Answer 26

• Acidity of Hydrogens bonded to Carbon
  C-H bond normally stable, non-polar and non-acidic
• Delocalisation of the resulting negative charge stablises the enolate anion and favours formation

Question 27

Tautomerism

Answer 27

• Isomerisation occouring by migration of a proton and the movement of double bond
• Turn into double bond carbon with alcohol

Question 28

Keto-Enol Tautomism

Answer 28

• Keto to protonate carbonyl to enol in basic machanism