Formaldehyde

H₂C=O

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Deuterium and Oxygen

Nuclear Quadrupole Coupling Constants

in Formaldehyde

Deuterium [1,2] and ¹⁷O [3,4] nqcc's have been measured in formaldehyde by Tucker and Tomasevich [1], Flygare [2], Cornet, Landsberg, and Winnewisser [3], and Flygare and Lowe [4]. Equilibrium molecular structures were reported by Carter and Handy [5] and Yamada, Nakagawa, Kutchitsu, and Morino [6].

Calculation was made here of the deuterium and oxygen nqcc's on the equilibrium structure of Yamada et al. These calculated nqcc's are compared with the experimental values in Tables 1 - 3. Structure parameters [5,6] are compared in Table 4.

In Table 1, the subscripts a,b,c refer to the principal axes of the inertia tensor, the subscripts x,y,z to the principal axes of the nqcc tensor. The nqcc y-axis is chosen coincident with the inertia c-axis. Ø (degrees) is the angle between its subscripted parameters. ETA = (X_xx - X_yy)/X_zz.


Table 1. Deuterium nqcc's in D₂C=O(kHz). Calculation was made on the equilibrium structure of Yamada et al. [6].

			Calc.		Expt. [1]

²H	X_aa		- 13.9		- 12.53(10)
	X_bb		97.1		97.23(10)
	X_cc		- 83.2		- 84.70(10)
	X_bc	±	113.7	±	107(2)

	RMS		1.2 (1.8 %)
	RSD		1.1 (0.9 %)

	X_xx		- 84.9
	X_yy		- 83.2
	X_zz		168.1
	ETA	-	0.010
	Ø_z,b		58.00
	Ø_b,CD		58.38
	Ø_z,CD		0.38


Table 2. Oxygen nqcc's in H₂C=O(MHz). Calculation was made on the equilibrium structure of Yamada et al. [6].

Calc. = B1LYP/6-311++G(3df,3p).

			Calc.		Expt. [1]

¹⁷O	X_aa		- 1.937		- 1.900(118)
	X_bb		12.408		12.35(52)
	X_cc	-	10.470	-	10.45(48)

	RMS		0.041 (0.50 %)
	RSD		0.041 (1.4 %)


Table 3. Oxygen nqcc's in H₂C=O(MHz). Calculation was made on the equilibrium structure of Yamada et al. [6].

Calc. = MP4(SDQ)/6-311++G(3df,3pd).

			Calc.		Expt. [1]

¹⁷O	X_aa		- 1.893		- 1.900(118)
	X_bb		12.325		12.35(52)
	X_cc	-	10.431	-	10.45(48)

	RMS		0.018 (0.22 %)
	RSD		0.022 (0.77 %)