Ethyl cyanoformate

CH₃CH₂-O-C(=O)CN

Nitrogen

Nuclear Quadrupole Coupling Constants

in Ethyl Cyanoformate

The microwave spectrum of ethyl cyanoformate was observed and assigned by True et al. [1-3].

For each conformer shown below, calculation of the nitrogen nqcc tensor was made on a molecular structure given by MP2/6-311+G(3df,3pd) optimization with empirically corrected approximate equilibrium C-C, C=O, and CN bond lengths. These calculated nqcc's are given in Tables 1 and 2. Structure parameters are given in Z-Matrix format in Table 3, rotational constants and dipole moments in Table 4.

syn-anti

syn-gauche

At the

MP2/6-311+G(3df,3pd)

level of theory,

E_syn-gauche < E_syn-anti

by 0.09 kJ/mol

O=COC Dihedral = 0^o

O=COC Dihedral = 1.2^o

COCC Dihedral = 180^o

COCC Dihedral = 81.3^o

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 = (X_xx - X_yy)/X_zz. Ø (degrees) is the angle between its subscripted parameters.

RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen efg's/nqcc's.


Table 1. Nitrogen nqcc tensor in syn-anti ethyl cyanoformate (MHz). Calculation was made on a molecular structure given by MP2/6-311+G(3df,3pd) optimization with approximate r_e C-C, C=O, and CN bond lengths.

			Calc.	Expt.

¹⁴N	X_aa	-	2.992
	X_bb		0.182
	X_cc		2.810
	X_ab	-	2.830

	RSD		0.030 (1.3 %)

	X_xx		1.840
	X_yy		2.810
	X_zz	-	4.650
	ETA		0.209
	Ø_z,a		30.36
	Ø_a,CN		29.89
	Ø_z,CN		0.47


Table 2. Nitrogen nqcc tensor in syn-gauche ethyl cyanoformate (MHz). Calculation was made on a molecular structure given by MP2/6-311+G(3df,3pd) optimization with approximate r_e C-C, C=O, and CN bond lengths.

			Calc.	Expt.

¹⁴N	X_aa	-	3.918
	X_bb		1.301
	X_cc		2.617
	X_ab	-	1.765
	X_ac		1.152
	X_bc		0.236

	RSD		0.030 (1.3 %)

	X_xx		1.830
	X_yy		2.818
	X_zz	-	4.648
	ETA		0.212
	Ø_z,CN		0.51


Table 3. Ethyl cyanoformate. MP2/6-311+G(3df,3pd) optimized structure parameters (Å and degrees). Approximate r_e bond lenths are given in parentheses.

syn-anti				syn-gauche
		C O,1,B1 O,1,B2,2,A1 C,1,B3,2,A2,3,D1,0 N,4,B4,1,A3,2,D2,0 C,3,B5,1,A4,2,D3,0 C,6,B6,3,A5,1,D4,0 H,6,B7,3,A6,1,D5,0 H,6,B8,3,A7,1,D6,0 H,7,B9,6,A8,3,D7,0 H,7,B10,6,A9,3,D8,0 H,7,B11,6,A10,3,D9,0

	B1=1.20471976 (1.2008) B2=1.32811632 B3=1.46700280 (1.4675) B4=1.17001338 (1.1565) B5=1.45008865 B6=1.50602743 (1.5047) B7=1.08801166 B8=1.08801166 B9=1.08803989 B10=1.08683591 B11=1.08683591 A1=126.95579738 A2=123.04619041 A3=177.15730186 A4=114.52914432 A5=106.81973633 A6=108.13392819 A7=108.13392819 A8=109.33553580 A9=110.70347787 A10=110.70347787 D1=-180.00000000 D2=-0.00000000 D3=0.00000000 D4=180.00000000 D5=58.64860660 D6=-58.64860660 D7=180.00000000 D8=-60.40718153 D9=60.40718153		B1=1.20531953 (1.2014) B2=1.32736727 B3=1.46724711 (1.4678) B4=1.1700948 (1.1566) B5=1.45084311 B6=1.5103975 (1.5088) B7=1.08727194 B8=1.08522011 B9=1.08880547 B10=1.08673928 B11=1.08740752 A1=127.32388467 A2=122.80514564 A3=177.04916456 A4=115.02889696 A5=110.60095442 A6=108.45379935 A7=103.67652818 A8=109.24527157 A9=110.7781895 A10=110.50131488 D1=-179.78395128 D2=-1.93158455 D3=1.22933198 D4=81.26807515 D5=-41.71704198 D6=-158.50745355 D7=176.26378994 D8=-64.4413217 D9=56.94023387


Table 4. Ethyl cyanoformate, rotational constants (MHz) and dipole moments (D).

		________syn-anti_________		_______syn-gauche________
		Calc	Expt [1]	Calc	Expt [1]

	A	6499	6453.3(4)	6831	6787.8(7)
	B	1507	1500.47(6)	1564	1549.38(8)
	C	1242	1236.36(6)	1421	1406.80(8)

	\|µ_a\|	4.54	4.44(7)	4.38	4.25(7)
	\|µ_b\|	0.03	~ 0	0.79	~ 0
	\|µ_c\|	0 (symm)	0 (symm)	0.52	1.08(23)

[1] R.D.Suenram, N.S.True, and R.K.Bohn, J.Mol.Spectrosc 69,435(1978).

[2] N.S.True and R.K.Bohn, OSU International Symposium on Molecular Spectroscopy, 1975.

[3] N.S.True, J.Phys.Chem. A 110,7364(2006).

Vinyl Chloroformate

S-Methylchlorothioformate

Methyl Chloroformate

Ethyl Carbamate I

Methyl Carbamate

CH3CH2OCOCN.html

Last Modified 16 Jan 2014