Chemistry Reference
In-Depth Information
Table 2.8
Computationally estimated PAs and pK
a
values for guanidine proton sponges
Me
2
N
NMe
2
Me
2
N
Me
Me
NMe
2
NMe
2
NMe
2
N
N
NMe
2
Me
2
N
N
N
Me
2
N
NMe
2
Me
2
N
N
N
N
NMe
2
N
N
N
N
N
Me
Me
X
TMGN
TMGF
DMEGN
80
: X = CH=CH
81
: X= CH
2
CH
2
82
: 2 x X = H
NMe
2
NMe
2
Me
Me
Me
2
N
NMe
2
Me
2
N
N
N
N
N
NMe
2
N
N
Me
2
N
NMe
2
N
N
N
N
Me
Me
Me
Me
N
N
N
85
N
N
N
M
e
Me
83
84
NMe
2
Me
2
N
NMe
2
R
Me
2
N
NMe
2
Me
2
N
N
NMe
2
N
N
86
87
88
PA (MP2)
a
PA (HF
SC
)
b
p
K
a
(MeCN)
theor
c
80
268.2
264.7
29.0
81
266.8
264.0
28.8
82
263.8
260.0
25.9
TMGF
263.7
27.8
TMGN
257.5
25.4 (25.1)
83
260.5
260.1
24.4
84
256.0
257.8
25.8
85
254.3
253.3
24.0
86
average
240.3-250.3
243.6-252.7
18.0-20.7
87
253.8
24.6
88
252.0
251.8
DMEGN
250.8
252.3
23 (TMGN
>
DMEGN)
DMAN
245.5
19.9 (18.2)
TMPhG
245.1
21.1 (20.6)
TMG
244.6
23.7 (23.6)
guanidine
233.7
24.1
a
MP2(fc)/6-311
þ
G**//HF/6-31G*
þ
ZPVE(HF/6-31G*).
b
Scaled HF/6-31G*.
c
IPCM-B3LYP/6-311
þ
G**//HF/6-31G* (experimental values are given in brackets).
