Carbenes & Nitriles

Question 1

carbenes

Answer 1

neutral, divalent, highly reactive carbon intermediates that have 2 non-bonding electrons

sp2

Question 2

how many spin states exist for the non-bonding electrons in carbenes?

Answer 2

2 - paired or parallel

Question 3

carbene - singlet vs triplet

Answer 3

triplet = more stable

triplet state has two unpaired e-, singlet = 1 pair of electrons

Question 4

carbenes - reactivity

Answer 4

electron deficient (only 6 electrons) -> highly electrophilic

presence of EW R groups increases electrophilicity

use of strong 𝛑-donor sub. enables carbene to react as a nucleophile (stabilises singlet state)

Question 5

metal-carbene complexes

Answer 5

less reactive than free carbenes (allows you to control selectivity)

rhodium complexes = most popular (due to selectivity and ease of catalyst modification)

air stable and easy to handle

Question 6

nitrenes

Answer 6

6 e-, neutral, monovalent, highly reactive nitrogen intermediates with 4 non-bonding electrons