6.1.2 - 6.1.3 - carbonyls, carboxylic acids and esters

Question 1

what is a carbonyl?

Answer 1

contain a C-O double bond and are either aldehydes or ketones

Question 2

describe the orbital overlaps in a carbonyl C-O bond

Answer 2

sideways overlap of the p-orbitals on C and O form a pi-bond above and below the plane of the C-O sigma bond.

Question 3

describe the polarity of a C-O double bond in a carbonyl

Answer 3

O is more electronegative than carbon, there is a permanent dipole across the bond resulting in a polar bond.

Question 4

describe the partial oxidation of a primary alcohol.

Answer 4

distil with H2SO4 and K2Cr2O7 (represented as [O] in equations). one molar equivalent of [O] is required. forms aldehyde and 1 mol of water. colour change from orange to green.

Question 5

describe the complete oxidation of a primary alcohol.

Answer 5

reflux with H2SO4 and K2Cr2O7 (represented as [O] in equations). two molar equivalents of [O] is required. forms carboxylic acid and 1 mol of water. colour change from orange to green.

Question 6

describe the complete oxidation of a secondary alcohol.

Answer 6

distil or reflux with H2SO4 and K2Cr2O7 (represented as [O] in equations). one molar equivalent of [O] is required. forms ketone and 1 mol of water. colour change from orange to green.

Question 7

describe the oxidation of a tertiary alcohol

Answer 7

tertiary alcohols cannot be oxidised. when refluxed with K2Cr2O7, colour remains orange.

Question 8

what is the name of the mechanism that converts carbonyls to alcohols

Answer 8

nucleophilic addition (of H-)

Question 9

what reagents are needed in the reduction of a carbonyl to form an alcohol

Answer 9

NaBH4 and H2O (warmed). NaBH4 is represented and [H] in the equation and 2[H] is needed for every C-O double bond reduced.

Question 10

in the reduction of a carbonyl by nucleophilic addition, what is the nucleophile and what is the electrophile?

Answer 10

H- acts as the nucleophile and the carbonyl is the elctrophile.

Question 11

what kind of bond breaking occurs in nucleophilic addition (of H-) (with a carbonyl)

Answer 11

heterolytic fission. both e- in the covalent bond go to the more electronegative of the 2 atoms.

Question 12

in the nucleophilic addition of CN-, how is the nucleophile formed?

Answer 12

CN- is the nucleophile. HCN is generated “in situ” by reacting H2SO4 with aqueous NaCN.

Question 13

describe the test for aldehydes and ketones and what a positive result looks like.

Answer 13

add 2,4-DNPH (2,4 - dinitrophenylhydrazine) aka Brady’s reagent. and orange hydrazone precipitate indicates the presence of an either aldehyde or ketone

Question 14

why are carboxylic acids soluble in water?

Answer 14

they have hydrogen bonding

Question 15

why do carboxylic have relatively high boiling points?

Answer 15

they have hydrogen bonding

Question 16

why does solubility of carboxylic acids decrease as chain length increases?

Answer 16

the alkyl chain is not soluble

Question 17

what is the equation of the partial dissociation of a carboxylic acid and what is the name of the ion formed?

Answer 17

C3CHHO –> CH3COO- +H+
ethanoate ion

Question 18

give the relative reactivities of an alcohol, phenol and carboxylic acid with Na, NaOH and Na2CO3

Answer 18

Na - reacts with all 3
NaOH - reacts with phenols and Carboxylic acids
Na2CO3 - only reacts with carboxylic acids

Question 19

what does the reaction of an alcohol and carboxylic acid in the presence of a conc H2SO4 catalyst produce? what kind of reaction is it

Answer 19

condensation reaction. produced an ester and water

Question 20

give 2 uses of esters

Answer 20

food flavourings and perfumes

Question 21

what is the yield of the reaction of an acid anhydride and alcohol relative to the reaction of a carboxylic acid and an alcohol

Answer 21

better yield

Question 22

how is an acid anhydride made

Answer 22

in the condensation reaction of 2 carboxylic acids

Question 23

what do you react with an acid anhydride to make an ester and carboxylic acid?

Answer 23

alcohol

Question 24

what is hydrolysis?

Answer 24

reaction with water to break down a compound.

Question 25

what is the reactant and what are the reaction conditions in the hydrolysis of an ester

Answer 25

H2O reactant, HCl and reflux as conditions

Question 26

what is the reactant and what are the reagents in alkaline hydrolysis of an ester

Answer 26

NaOH reactant, H2O and reflux conditions

Question 27

in a base hydrolysis, the carboxylic acid produced is neutralised to ________

Answer 27

carboxylate salt

Question 28

what is an acyl chloride?

Answer 28

Cl atom attached to the carbonyl carbon

Question 29

how are acyl chlorides produced?

Answer 29

reaction of a carboxylic acid and thionyl chloride (SOCl2)

Question 30

what mechanism do acyl chlorides undergo?

Answer 30

nucleophilic substitution

Question 31

in the reaction of an acyl chloride and ammonia, how many molar equivalents are required to react with 1 mol of acyl chloride?

Answer 31

2 moles

Question 32

when an acyl chloride is reacted with ammonia, why are 2 molar equivalents of ammonia required?

Answer 32

with the first mole of NH3, HCl is produced. a second mole is required to neutralise the HCl to make NH4Cl otherwise the HCl would protonate the amide.

Question 33

when an acyl chloride reacts with a primary amine, what letter is placed in front of the name of the organic product to indicate it is a secondary amine?

Answer 33

N

Question 34

how many molar equivalents of the amine are required per mole of acyl chloride?

Answer 34

2

Question 35

why are 2 molar equivalent of amine required when reacting with an acyl chloride?

Answer 35

2nd equivalent is required to neutralise the HCl and produces an ammonium salt.