nucleophilic addition - chapter 6

Question 1

when a nucleophile attacks the carbonyl group which orbital do the electrons enter

Answer 1

the pi* orbital, which breaks the carbonyl bond

Question 2

how does the electron pair entering the pi* orbital cause the pi bond to break

Answer 2

the electrons break the pi system, destabilising the bond

Question 3

when the carbonyl bond breaks, where are the electrons transferred

Answer 3

onto the oxygen which forms a negative charge

Question 4

why are aldehydes more reactive than ketones

Answer 4

1. steric hindrance - ketones have two R groups thus having a larger steric hindrance than aldehydes
2. aldehydes have one less R group attached to the carbonyl bond - there is less + inductive effect therefore the delta positive charge on the

Question 5

what is the most important factor to consider when deciding how acidic a molecule is

Answer 5

its resonance structures

Question 6

why are organometallic reagents powerful nucleophiles

Answer 6

due to the great difference in electronegativities between the carbon group and the metal, the bond is very polar

Question 7

what effect does protonating the carbonyl group have on a molecule

Answer 7

it makes the carbon more electrophilic
it increases the rate of the reaction
this makes it more attractive for the nucleophile

Question 8

what does an acid catalyst contribute to a nucleophilic reaction

Answer 8

it protonates the carbonyl group, making the carbonyl more electrophilic

Question 9

what does having a basic catalyst contribute to a nucleophilic reaction

Answer 9

it de-protonates the nucleophile, making the nucleophile more nucleophilic

Question 10

why is sodium bisulphate added to aldehydes and ketones

Answer 10

for purification

sulfur atom has lone pair