6.1.2 - 6.1.3 - carbonyls, carboxylic acids and esters Flashcards
what is a carbonyl?
contain a C-O double bond and are either aldehydes or ketones
describe the orbital overlaps in a carbonyl C-O bond
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.
describe the polarity of a C-O double bond in a carbonyl
O is more electronegative than carbon, there is a permanent dipole across the bond resulting in a polar bond.
describe the partial oxidation of a primary alcohol.
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.
describe the complete oxidation of a primary alcohol.
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.
describe the complete oxidation of a secondary alcohol.
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.
describe the oxidation of a tertiary alcohol
tertiary alcohols cannot be oxidised. when refluxed with K2Cr2O7, colour remains orange.
what is the name of the mechanism that converts carbonyls to alcohols
nucleophilic addition (of H-)
what reagents are needed in the reduction of a carbonyl to form an alcohol
NaBH4 and H2O (warmed). NaBH4 is represented and [H] in the equation and 2[H] is needed for every C-O double bond reduced.
in the reduction of a carbonyl by nucleophilic addition, what is the nucleophile and what is the electrophile?
H- acts as the nucleophile and the carbonyl is the elctrophile.
what kind of bond breaking occurs in nucleophilic addition (of H-) (with a carbonyl)
heterolytic fission. both e- in the covalent bond go to the more electronegative of the 2 atoms.
in the nucleophilic addition of CN-, how is the nucleophile formed?
CN- is the nucleophile. HCN is generated “in situ” by reacting H2SO4 with aqueous NaCN.
describe the test for aldehydes and ketones and what a positive result looks like.
add 2,4-DNPH (2,4 - dinitrophenylhydrazine) aka Brady’s reagent. and orange hydrazone precipitate indicates the presence of an either aldehyde or ketone
why are carboxylic acids soluble in water?
they have hydrogen bonding
why do carboxylic have relatively high boiling points?
they have hydrogen bonding
why does solubility of carboxylic acids decrease as chain length increases?
the alkyl chain is not soluble
what is the equation of the partial dissociation of a carboxylic acid and what is the name of the ion formed?
C3CHHO –> CH3COO- +H+
ethanoate ion
give the relative reactivities of an alcohol, phenol and carboxylic acid with Na, NaOH and Na2CO3
Na - reacts with all 3
NaOH - reacts with phenols and Carboxylic acids
Na2CO3 - only reacts with carboxylic acids
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
condensation reaction. produced an ester and water
give 2 uses of esters
food flavourings and perfumes
what is the yield of the reaction of an acid anhydride and alcohol relative to the reaction of a carboxylic acid and an alcohol
better yield
how is an acid anhydride made
in the condensation reaction of 2 carboxylic acids
what do you react with an acid anhydride to make an ester and carboxylic acid?
alcohol
what is hydrolysis?
reaction with water to break down a compound.
what is the reactant and what are the reaction conditions in the hydrolysis of an ester
H2O reactant, HCl and reflux as conditions
what is the reactant and what are the reagents in alkaline hydrolysis of an ester
NaOH reactant, H2O and reflux conditions
in a base hydrolysis, the carboxylic acid produced is neutralised to ________
carboxylate salt
what is an acyl chloride?
Cl atom attached to the carbonyl carbon
how are acyl chlorides produced?
reaction of a carboxylic acid and thionyl chloride (SOCl2)
what mechanism do acyl chlorides undergo?
nucleophilic substitution
in the reaction of an acyl chloride and ammonia, how many molar equivalents are required to react with 1 mol of acyl chloride?
2 moles
when an acyl chloride is reacted with ammonia, why are 2 molar equivalents of ammonia required?
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.
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?
N
how many molar equivalents of the amine are required per mole of acyl chloride?
2
why are 2 molar equivalent of amine required when reacting with an acyl chloride?
2nd equivalent is required to neutralise the HCl and produces an ammonium salt.
