|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
CH3N(H)C(CH3)(COOH) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Nitrogen |
|
|
|
Nuclear
Quadrupole Coupling Constants |
|
|
|
in N-Methyl-L-Alanine
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Calculations of the nitrogen nqcc
tensors in N-methyl-L-alanine was made on MP2/6-311++G(d,p) optimized molecular structures (ropt) derived by Neeman et al. [1]
of the conformers shown below. These are two of four different
conformers observed in the microwave spectrum [1].
These calculated nqcc's are compared with the experimental
results in Tables 1 and 2.
|
|
|
|
|
|
|
|
|
|
|
|
|
Conformer IIa
|
|
|
Conformer IIc
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
In Tables 1 and 2, subscripts a,b,c
refer to the
principal axes of the inertia tensor; x,y,z to the principal axes
of the nqcc tensor. ETA = (Xxx - Xyy)/Xzz.
|
|
|
RMS is the root mean square
difference between calculated and experimental diagonal nqcc's
(percentage of the average of the magnitudes of the experimental
nqcc's). RSD is the calibration residual standard deviation for
the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen efg's/nqcc's. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
|
|
|
|
|
|
|
|
Table 1. Nitrogen
nqcc's in Conformer IIa of N-methyl-L-alanine (MHz). Calculation was made on ropt = MP2/6-311++G(d,p) molecular strcuture. |
|
| |
|
|
|
|
|
|
|
|
|
|
|
Calc
|
|
Rotamer 2 [1] |
|
| |
|
|
|
|
|
|
|
|
14N |
Xaa |
|
1.868
|
|
1.871(9)
|
|
|
|
Xbb |
|
0.500
|
|
0.492(9)
|
|
|
|
Xcc |
-
|
2.368
|
-
|
2.362(9)
|
|
|
|
Xab |
|
1.309
|
|
|
|
|
|
Xac |
-
|
1.640
|
|
|
|
|
|
Xbc |
|
2.812
|
|
|
|
|
|
|
|
|
|
|
|
|
|
RMS
|
|
0.006 (0.40 %)
|
|
|
|
|
|
RSD
|
|
0.030 (1.3 %) |
|
|
|
|
|
|
|
|
|
|
|
|
|
Xxx |
|
2.084
|
|
|
|
|
|
Xyy |
|
2.663
|
|
|
|
|
|
Xzz |
-
|
4.748
|
|
|
|
|
|
ETA
|
|
0.122
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
|
|
|
|
|
|
|
|
Table 2. Nitrogen
nqcc's in Conformer IIc of N-methyl-L-alanine (MHz). Calculation was made on ropt = MP2/6-311++G(d,p) molecular strcuture. |
|
| |
|
|
|
|
|
|
|
|
|
|
|
Calc
|
|
Rotamer 3 [1] |
|
| |
|
|
|
|
|
|
|
|
14N |
Xaa |
|
1.197
|
|
1.209(4)
|
|
|
|
Xbb |
-
|
3.302
|
-
|
3.255(9)
|
|
|
|
Xcc |
|
2.105
|
|
2.046(9)
|
|
|
|
Xab |
-
|
2.896
|
|
|
|
|
|
Xac |
|
0.159
|
|
|
|
|
|
Xbc |
|
1.084
|
|
|
|
|
|
|
|
|
|
|
|
|
|
RMS
|
|
0.044 (2.0 %)
|
|
|
|
|
|
RSD
|
|
0.030 (1.3 %) |
|
|
|
|
|
|
|
|
|
|
|
|
|
Xxx |
|
2.064
|
|
|
|
|
|
Xyy |
|
2.812
|
|
|
|
|
|
Xzz |
-
|
4.876
|
|
|
|
|
|
ETA
|
|
0.153
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
[1] E.M.Neeman, I.León, E.R.Alonso, L.Kolesniková, S.Mata, and J.L.Alonso, PCCP, 20,29159(2018).
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Table of Contents |
|
|
|
|
|
Molecules/Nitrogen |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
NMLA.html |
|
|
|
|
|
|
Last
Modified 10 Dec 2018 |
|
|
|
|
|
|
|
|
|
|