Benzene-d1

C₆H₅D

Deuterium

Nuclear Quadrupole Coupling Constants

in Benzene-d₁

Deuterium nqcc's in monodeuterated benzene were measured by Jans-Bürli, M.Oldani, and A.Bauder [1].

Langseth and Stoicheff [2] by rotational Raman spectroscopy determined a benzene structure in which CC = 1.3973 Å and CH = 1.084 Å. Oldani and Bauder [3] by MW spectroscopic investigation of the monodeuterated molecule determined CC =1.395 Å and CH = 1.082 Å. More recently, Caminati et al. [4] determined from the rotational constants of several isotopomers a structure in which CC = 1.3974 Å and CH = 1.0788 Å. Optimization with the B3P86/6-31G(3d,3p) model yields CC = 1.3909 and CH = 1.0851 Å.

We investigate here the sensitivity of the deuterium nqcc's to the molecular structure. First, in Table 1, comparison is made between the experimental nqcc's and those calculated on the B3P86/6-31G(3d,3p) molecular structure. Then, with CH fixed at the optimization value, the nqcc's are calculated as functions of CC bond length. These are shown in Table 2. It is seen that the calculated nqcc's are not sensitive to the CC bond length. Now, CC is held fixed at the optimization value, while CH is varied. These calculated nqcc's are shown in Table 3.

In Table 4, nqcc's calculated on B3P86/6-31G(3d,3p) structures of benzene, fluorobenzene, and phenylacetylene are compared.

In Tables 1 - 3, RMS is the root mean square difference between calculated and experimental inertia axes nqcc's (percentage of the average of the magnitudes of the experimental nqcc's). RSD is the calibration residual standard deviation for the B3LYP/6-31G(df,3p) model for calculation of the nqcc's.


Table 1. Deuterium nqcc's in Benzene-d₁ (kHz). Calculation was made on the B3P86/6-31G(3d,3p) structure. Note: Experimental X_bb and X_cc are here interchanged [5].

		Calc.	Expt. [1]

²H	X_aa	189.0	186.1(18)
	X_bb	- 89.0	- 88.9(23)
	X_cc	- 99.9	- 97.2(23)

	RMS	2.3 (1.8 %)
	RSD	1.1 (0.9 %)


Table 2. Dependence of the deuterium nqcc's (kHz) in benzene on CC bond length. CH = 1.0851 Å.

CC (Å)	X_zz	X_yy	X_xx	RMS

1.3859	189.0	-89.1	-99.8	2.2
1.3909	189.0	-89.1	-99.9	2.3
1.3959	189.0	-89.2	-99.9	2.3
1.4009	189.1	-89.2	-99.9	2.3
1.4059	189.1	-89.2	-100.0	2.4


Table 3. Dependence of the deuterium nqcc's (kHz) in benzene on CH bond length. CC = 1.3909 Å.

CH (Å)	X_zz	X_yy	X_xx	RMS

1.079	196.0	-92.6	-103.4	7.1
1.081	193.7	-91.5	-102.2	5.5
1.083	191.4	-90.3	-101.1	3.9
1.085	189.1	-89.2	-99.9	2.3
1.087	186.9	-88.1	-98.8	1.1
1.089	184.6	-87.0	-97.7	1.4
1.091	182.4	-85.9	-96.6	2.8

Expt. [1]	186.1(18)	-88.9(23)	-97.2(23)


Table 4. Principal values of the deuterium nqcc tensor calculated on the B3P86/6-31G(3d,3p) optimized structures of phenylacetylene (PhA), fluorobenzene (FB), and benzene. (kHz and degrees)

	X_zz	X_yy	X_xx	ETA	Ø_z,CD

C₆H₅D	189.0	-99.9	-89.1	0.057	0

PhA D(4)	188.9	-99.7	-89.1	0.056	0
FB D(4)	190.0	-101.1	-88.8	0.065	0

PhA D(3)	188.8	-99.7	-89.0	0.057	0.01
FB D(3)	188.7	-99.6	-89.2	0.055	0.03

PhA D(2)	188.3	-99.8	-88.6	0.059	0.20
FB D(2)	190.0	-100.8	-89.2	0.061	0.29

[1] S.Jans-Bürli, M.Oldani, and A.Bauder, Mol.Phys. 68,1111(1989).

[2] A.Langseth and B.P.Stoicheff, Can.J.Phys. 34,350(1956).

[3] M.Oldani and A.Bauder, Chem.Phys.Lett. 108,7(1984).

[4] W.Caminati, S.DiBernardo, L.Schäfer, S.Q.Kulp-Newton, and K.Siam, J.Mol.Struct. 240,263(1990).

[5] W.C.Bailey, J.Mol.Spectrosc. 190,318(1998).

"Deuterium quadrupole coupling in benzene: librational corrections ..." P.Pyykkö and F.Elmi, PCCP 10,3867(2008).

C6H5D.html

Last Modified 2 June 2003