The Hammet Relationship

Question 1

Hammet relationship

Answer 1

Quantifies effect that EDG/EWG have on TS/intermediate during a reaction

Question 2

How is Hammet relationship measured

Answer 2

Uses phenyl group with substituents as a probe

Question 3

Hammet substituent constant

Answer 3

σ, shows magnitude of EDG/EWG relative to H, 0 = no effect, +ve = EWG, -ve = EDG

Question 4

Location of substituents

Answer 4

Para and meta only as ortho complicated by sterics

Question 5

Inductive withdrawing

Answer 5

Electronegative elements pulls electron density towards itself, -I

Question 6

Inductive donating

Answer 6

Any alkyl group, no lone pair but donates electron density through hyperconjugation

Question 7

Mesomeric donating

Answer 7

Donates electron density through resonance

Question 8

Mesomeric withdrawing

Answer 8

Removes electron density through π-conjugated withdrawing groups

Question 9

I dependent on

Answer 9

Distance

Question 10

Hammet reaction constant

Answer 10

ρ, gradient when log(Kx/kH) plotted against σ

Question 11

Positive ρ

Answer 11

More electron density in TS than SM at RDS, -ve charge build up at TS so TS stabilised by EWG

Question 12

Negative ρ

Answer 12

less electron density in TS than SM at RDS, +ve charge build up at TS so TS stabilised by EDG

Question 13

Magnitude of ρ

Answer 13

Full -ve charge at TS gives larger +ve value of ρ, also affected by distance of sub phenyl ring from charge

Question 14

Change in RDS Hammet plot

Answer 14

Sad face

Question 15

Change in mechanism/TS Hammet plot

Answer 15

Happy face