Lise Hansen-Nygaard

The structure of thiophene

Abstract The microwave spectra of 2- C 13 -thiophene and of 3- C 13 -thiophene have been recorded and analyzed. In addition, three lines from the S 34 -thiophene were found and identified. Taken together with earlier published data for thiophene, thiophene-2 d , and thiophene-3 d , an unambiguous calculation of the (‘ r 8 ’-) structure of thiophene is now possible, the structural parameters being: (distances) CS = 1.714 A; CC = 1.370A; CC = 1.423 A; C(2)H(2) = 1.078 A; C(3)H(3) = 1.081 A; (angles) C(5)SC(2) = 92°10′; SC(2)C(3) = 111°28′; C(2)C(3)C(4) = 112°27′; SC(2)H(2) = 119°51′; C(4)C(3)H(3) = 124°16′.

The complete structure of furan

Abstract Microwave spectra of [2- 13 C] furan, [3- 13 C] furan, and [ 18 O] furan are reported. Moments of inertia of these species are combined with earlier data on furan and deuterated furans to give the r s -structure of furan. The final structure is: OC(2) = 1.362 A, C(2)C(3) = 1.361 A, C(3)C(4) = 1.431 A, C(2)H(2) = 1.075 A, C(3)H(3) = 1.077 A, C(5)OC(2) = 106°33′, OC(2)C(3) = 110°41′, C(2)C(3)C(4) = 106°3′, OC(2)H(2) = 115°55′, C(4)C(3)H(3) = 127°57′.

Complete determination of the structure of pyridine by microwave spectra

Abstract Isotopic mixtures of ordinary pyridine and 2- 13 C- and 3- 13 C-pyridine have been prepared and the microwave spectra recorded. For 2- 13 C- and 3- 13 C-pyridine, respectively, 12 and 10 transitions ( Q - and R -branch lines) were localized, a number of which could be identified by their Stark-effect. For both 13 C-species rotational constants of high precision were calculated. These constants together with known rotational constants for ordinary pyridine, 2 D -, 3 D -, and 4 D -pyridine are sufficient for a complete determination of the ten geometrical parameters of the molecule. The interatomic distances in the model finally adopted are: d [NC(2)] = 1.3402, d [C(2)C(3)] = 1.3945, d [C(3)C(4)] = 1.3944, d [C(2)H(2)] = 1.0843, d [C(3)H(3)] = 1.0805, and d [C(4)H(4)] = 1.0773 A. The valence angles in the aromatic ring [starting with the C(6)NC(2) angle] are: 116°50′, 123°53′, 118°32′, and 118°20′. The distances are thought to be correct to ±0.001A.

Benzene Ring Distortion by One Substituent. Microwave Determination of the Complete Structure of Benzonitrile

Microwave spectra of benzonitrile, C6H5CN, and 9 isotopic species are reported. Moments of inertia of these 10 molecules are combined to give the rs structure of benzonitrile. The final structure is: C(1)C(2) = 1.391 A, C(2)C(3) = 1.393 A, C(3)C(4) = 1.400 A, C(1)C(7) = 1.455 A, C≡N = 1.159 A, C(2)H(2) = 1.069 A, C(3)H(3) = 1.082 A, C(4)H(4) = 1.081 A, C(6)C(1)C(2) = 122.5°, C(1)C(2)C(3) = 118.45°, C(2)C(3)C(4) = 120.3°, C(3)C(4)C(5) = 120.0°, C(1)C(2)H(2) = 121.8°, C(4)C(3)H(3) = 119.9°.

Microwave Determination of the Structure of Fluorobenzene

3D‐, 4D‐, and 2,4,6 D3‐fluorobenzene have been prepared. Their microwave spectra have been recorded and analyzed. Values of their rotational constants together with known values of the rotational constants of ordinary fluorobenzene do not suffice for an unambiguous calculation of the 11 geometrical parameters of the molecule but by assistance from valence theory a small number of fairly probable models may be pointed out.

The structure of vinyl fluoride

Abstract By means of microwave spectra of vinyl fluoride and five of its deuterated species the most probable structure of vinyl fluoride has been evaluated. This structure has C(1), F = 1·348 A; C(I), H(1) = 1·073 A; C(2), H(2) = 1·080 A; C(2), H(3) = 1·080 A; C(1), C(2) (double bond distance) = 1·333 A.

Molecular Structure Correlations

The molecular structure of methane, ethane, ethylene, acetylene, ethyl fluoride, benzene, butadiene, allene, butatriene, propylene, cyclooctatetraene, methyl acetylene, diacetylene, methyl cyanide, methyl isocyanide, vinyl cyanide, carbon dioxide, formaldehyde, acetaldehyde, propynal, acrolein, formic acid, methyl formate, formamide, and acetyl cyanide (25 molecules) have been correlated by means of a set of empirical parameters, the physical meaning of which is discussed in part.

Microwave determination of the structure of ethyl fluoride

Abstract Eleven isotopic ethyl fluorides were prepared and investigated by the microwave method. Since both carbon atoms and all hydrogens were successively substituted by 13 C and deuterium, the resulting structural determination is as complete as feasible at the moment. The geometrical parameters found are: The “staggered” conformation was unambiguously proved. In all cases where rotational isomerism was to be expected the correct number of isomers was found and the microwave spectrum of each “rotational” species was analysed.

Microwave spectra of 1,3,4-thiadiazole and [34S]1,3,4-thiadiazole. Dipole moment of 1,3,4-thiadiazole

Abstract The microwave spectra of 1, 3, 4-thiadiazole (I) and [ 34 S] 1, 3, 4-thiadiazole (II) have been recorded in the 15,000–30,000 Mc/sec region. Twelve and ten transitions, respectively, were assigned. The rotational constants of (I) are, A = 8907.51 ± 0.10, B = 5569.27 ± 0.02, and C = 3424.80 ± 0.03 Mc/sec. For (II), A = 8908.15 ± 0.20, B = 5408.54 ± 0.05, and C = 3363.31 ± 0.03 Mc/sec. The measured dipole moment of (I) in the ground state is 3.28 ± 0.03 debye.

The structure of tertiary butyl isocyanide

Abstract The structure of tert. butyl isocyanide is calculated from microwave measurements and an assumed structure of the tertiary butyl group. The carbon-nitrogen triple bond distance found is in excellent agreement with the corresponding distance in the isomeric tertiary butyl cyanide, methyl cyanide, and methyl isocyanide. The distribution of electronic charge in cyanide and isocyanide groups is briefly discussed.