Lecture 4-Carbene basics and synth

Question 1

What is a carbene

Answer 1

:CR2
Neutral species containing C with only 6 valence electrons
Electrophilic- insert into sigma and pi

Question 2

Singlet carbenes

Answer 2

two dots in same sp2 orb
no unpaired electron
RCR angle smaller

Question 3

Triplet carbenes

Answer 3

1 electron in p orb
1 electron in sp2 orb
2 upe
RCR larger

Question 4

Relative energies

Answer 4

R=alkyl
T=ground state S=excited (energy e-s together)

Metal carbenoids- always a singlet 
R=X s=ground state

Question 5

What does reactivity of the carbene depend on

Answer 5

R groups
way it was synthesised
capapility to convert between s and t

Question 6

4 main synthesis methods of carbene

Answer 6

1) Diazo
2) TsNhNH2
3) Chloroform
4) decarboxylation

Question 7

Diazo

Answer 7

Makes C(H)(C(O)R)

RC(O-)=C-N≡N
+hv/D–> carbene
+Rh/Cu –> carbenoid

1,3 +NR3 base
+N≡N-NTs
2 NN on 1,3 ->hv/ru

Question 8

TsNHNH2

Answer 8

tsk nana Naiome
Makes CR2
carbonyl
+TsNHNH2 + NaOME

N2 where O was
heat -> carbene
rh/cu-> carbenoid

Question 9

Chloroform

Answer 9

Makes C(Cl)(Cl)
HCl3
\+strong base (NaOH)- takes away an H 
\+{NR4}{Cl} takes away Cl
CCl2

Question 10

Decarboxylation

Answer 10

Makes C(X)(X)
X3C-CO2Na
-> Co2 NaX CCl2