CH2Br-CH2F
	Bromine
	Nuclear Quadrupole Coupling Constants
	in gauche 1-Bromo-2-Fluoroethane
	Bromine nqcc's in the gauche conformer of 1-bromo-2-fluoroethane were determined by Niide et al. [1].
	Calculation of the bromine nqcc tensors was made here on a molecular structure derived ab initio with bond length correction as discussed below.   These are compared with the experimental nqcc's [1] in Tables 1 and 2.  Structure parameters are given in Table 3, atomic coordinates in Table 4, and rotational constants in Table 5.
	In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor, subscripts x,y,z to the principal axes of the nqcc tensor.  Ø (degrees) is the angle between its subscripted parameters. ETA = (Xxx - Xyy)/Xzz.
	RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average absolute experimental nqcc).  RSD is the residual standard deviation of calibration of the B1LYP/TZV(3df,3p) model for calculation of the nqcc's.
	The algebraic signs of the off-diagonal nqcc's, which depend on the positive/negative sense of the a,b,c inertia axes, correspond here to the atomic coordinates given in Table 4.
	Table 1.  79Br nqcc's in gauche CH2BrCH2F (MHz).     Calc. Expt. [1]     79Br Xaa 266.57 266.4(17) Xbb - 12.07 -  11.8(9) Xcc - 254.50 - 254.6(19) Xab + 394.38 392.7(43) * Xac - 117.84 Xbc - 91.51   RMS 0.2 (0.11 %) RSD 1.58 (0.39 %)   Xxx - 278.05 Xyy - 294.34 Xzz 572.39 ETA 0.0284 Øz,CBr 0.48
	* Absolute value.
	Table 2.  81Br nqcc's in gauche CH2BrCH2F (MHz).     Calc. Expt. [1]     81Br Xaa 223.45 225.5(12) Xbb - 10.76 - 11.5(7) Xcc - 212.69 - 214.0(14) Xab + 329.28 336.5(31) * Xac - 98.39 Xbc - 76.25   RMS 1.5 (0.97 %) RSD 1.38 (0.40 %)   Xxx - 232.30 Xyy - 245.91 Xzz 478.21 ETA 0.0284 Øz,CBr 0.48
	* Absolute value.
	Molecular Structure
	The molecular structure was optimized at the MP2/6-311+G(d,p) level of theory.  The optimized C-C and C-F bond lengths respectively were corrected using equations obtained from linear regression of the data given in references [2] and [3].  The CH bond lengths were corrected using r = 1.001 ropt, where ropt is obtained by MP2/6-31G(d,p) optimization [4].  Interatomic angles are those given by MP2/6-311+G(d,p) optimization.
	For the C-Br bond length, optimization was made at the MP2/6-311+G(2d,p) level of theory of the C-Br equilibrium bond lengths in CH3Br, CH2Br2, HCCBr, and BrCN.  Linear regression of the calculated versus equilibrium bond lengths yields the following relationship, by which the C-Br was corrected:
			r = 0.9946 × ropt + 0.0001,   RSD = 0.0015 Å.
	The optimized C-Br bond length is 1.9446 Å which, after correction is 1.934 Å.
	Table 3.  Gauche 1-Bromo-2-Fluoroethane.  Heavy atom structure parameters (Å and degrees).  The complete structure is given here in Z-Matrix format.   BrC(1) 1.934 C(1)C(2) 1.503 C(2)F 1.3785 C(2)C(1)Br 112.03 C(1)C(2)F 110.40 BrC(1)C(2)F   66.51
	Table 4.  Gauche 1-Bromo-2-Fluoroethane.  Atomic coordinates.  Normal species.    a (Å)  b (Å)  c (Å) C(1) 0.5895 1.0015 - 0.3065 C(2) 1.8149 0.4743 0.3858 H(3) 0.3599 1.9985 0.0638 H(4) 0.7432 1.0338 - 1.3821 H(5) 2.6407 1.1767 0.2386 H(6) 1.6401 0.3250 1.4523 Br - 0.9620 - 0.1055 0.0215 F 1.1918 - 0.7346 - 0.1591
	Table 5.  Gauche 1-Bromo-2-Fluoroethane.  Rotational constants (MHz).  Normal species.   Calc. ropt    Expt. [1] A 12 630.3 12 547.013(44) B   2 236.4   2 218.112(7) C   2 014.2   1 998.444(7)
	[1] Y.Niide, I.Ohkoshi, M.Takano, and M.Hayashi, J.Mol.Spectrosc. 115,305(1986).
	[2] J.Demaison, J.Cosléou, R.Bocquet, and A.G.Lesarri, J.Mol.Spectrosc. 167,400(1994).
	[3] R.M.Villamañan, W.D.Chen, G.Wlodarczak, J.Demaison, A.G.Lesarri, J.C.López, and J.L.Alonso, J.Mol.Spectrosc. 171,223(1995).
	[4] J.Demaison and G.Wlodarczak, Structural Chem. 5,57(1994).
	Ethyl Bromide			1-Bromo-1-Fluoroethane
	Methyl Bromide			2-Bromoethanol
	2-Bromopropane
	Table of Contents
	Molecules/Bromine
						gCH2BrCH2F.html
						Last Modified 7 Aug 2006