Chemistry Reference
In-Depth Information
7a''
6a''
27a'
5a''
4a''
O
3a''
N
26a'
FIGURE 12.11.
Molecular orbitals involved in the electronic transitions of the triplet nitrene
3
3a
.
17
Source
: Reprinted with permission from Ref. 17. Copyright 2003 RSC Publishing.
The oxazirene
1
3a
was also directly detected upon photolysis of
1a
in solution
at room temperature using the TRIR
17,25,26
and LFP
18,100
techniques. At first, the
photolysis of
at room temperature was studied in acetonitrile-d
3
, cyclohexane, and
dichloromethane using the TRIR specroscopy.
17
Based on the calculations and
matrice isolation studies, as discussed earlier, the positive band at 1760 cm
1
(Fig. 12.12) was assigned to singlet species
1
3a
1a
. Additional evidence that the
1760 cm
1
band is due to a singlet species is that its rate of decay is completely
unaffected by oxygen.
17
The lifetime of
1
3a
was not affected by the initial
concentration of azide
1a
; changing the concentration of
1a
by a factor of six
does not affect the lifetime of
1
3a
. The lifetime of
1
3a
is determined by the solvent
and is equal to 5.6
s in cyclohexane (Fig. 12.13), and
about 300 ns in acetonitrile-d
3
.
17
The mechanisms of
1
3a
m
s in dichloromethane,
1
m
reactions with solvents are
discussed in more detail later in this chapter.
Ph
N
C
O + Ph
O
CN (traces)
O
27
2a
λ
= 254 nm
-N
2
Ph
C
O
λ
= 313 nm
N
3
1a
Ph
C
1
3a
N
SCHEME 12.12.
Photochemistry of benzoyl azide
1a
in argon matrix at 12 K.
17,19,99
