Dipole Moments In Benzene Research Articles

Electric Dipole Moments of Substituted 3 Aminomethylbenzoxazolin 2 Thiones

A series of substituted-3-aminomethylbenzoxazolin-2thiones have been synthesised and their electric dipole moments in benzene have been determined.

Solvent Effect on the Structure and Infrared Spectra of N-(3-Chloro-2-benzo[b]thienocarbonyl)-N'-ethylthiourea

The solvent effect on the title compound was studied by examining changes in the positions of IR bands belonging to the NH and CO bonds and in the dipole moments in benzene and dioxane solutions. The results are discussed in terms of intramolecular hydrogen bonding and spatial arrangement of the CONHCSNH grouping.

Dipole moments of some N-phenyl-substituted derivatives of pyrrolidine, piperidine, morpholine, and thiomorpholine

Apparent dipole moments in benzene of various p-substituted N-phenyl derivatives of pyrrolidine, piperidine, morpholine, and thiomorpholine and of some analogous NN-diethylanilines have been determined.

A dipole moment study of N-methyl and N,N-dimethyl-imidazolidin-2-ones, imidazolidine-2-thiones and -2-selenones

Abstract The electric dipole moments in benzene and dioxan of potentially tautomerizable N -methylimidazolidin-2-one, N -methylimidazolidine-2-thione and -2-selenone clearly support the lactam structure for these compounds. The fact that their dipole moments in dioxan are markedly greater than those in benzene is explained by a higher (HN-CY) mesomeric moment in the hydrogen-bonded solute · dioxan complexes. Analysis of the dipole moments in benzene of N , N -dimethylimidazolidin-2-one, N , N '-dimethylimidazolidine-2-thione and -2-selenone shows that the mesomeric moment (due to contribution of zwitterionic valence structures) gradually increases on going from Y = O to Y = S, and Y = Se. Finally, preferred conformations, from their dipole moments in benzene, are suggested for tetramethylurea and tetramethylthiourea.

Dipole moments of derivatives of 4-phenylazo-NN-diethylaniline and of 9-phenylazojulolidine (9-phenylazo-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizine)

Apparent dipole moments in benzene of a series of para-substituted derivatives of 9-phenylazojulolidine (9-phenylazo-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizine) have been determined together with those of the corresponding series derived from 4-phenylazo-NN-diethylaniline. Vector moments, µ(int), in the direction of the major axis of the molecules have been calculated in order to explain the observed moments. The values of µ(int) for the 9-phenylazojulolidines are all greater than those for the corresponding 4-phenylazo-NN-diethylanilines and, for both series of compounds, increase with increase in the Hammett substituent parameter, σp. Evidence is presented that the terminal nitrogen atom is more nearly planar in the 9-phenylazojulolidines than in the 4-phenyl-azo-NN-diethylanilines and also that µ(int) arises by interaction of the para-substituent with the π-electron distribution in the aromatic ring to which it is attached.

An experimental study of various arenetricarbonylchromium complexes

Abstract For a series of arenetricarbonylchromium complexes ZCr(CO) 3 , analysis of the electric dipole moments in benzene and carbonyl stretching frequencies in cyclohexane suggest the following: for unsubstituted ZCr(CO) 3 , with Z = diphenyl, fluorene and cis -stilbene, the π-basicity to be considered is that of the ring directly united to the tricarbonylchromium group, and not that of the arene as a whole. In general, the substituent effect in p -substituted diphenyltricarbonylchromium complexes (Z = 4-methyl-, 4-amino- and 4,4′-dimethyldiphenyl), in which the tricarbonylchromium group is bonded to the substituted phenyl ring, is markedly weaker than that in the corresponding benzenetricarbonylchromium complexes. In 4-fluorodiphenyltricarbonylchromium, the tricarbonylchromium group is attached to the unsubstituted phenyl ring. 4-Aminodiphenyltricarbonylchromium exists in two distinct forms: one with the nitrogen lone pair away from, and the other close to, the metal atom. Diphenylmethanetricarbonylchromium (and its 4,4′-diamino derivative), indanetricarbonyl- and 4,4′-difluorodiphenyltricarbonylchromium have also been examined.

Dipole moment study of the ortho-effect in 4-substituted NN-dimethyl-2-trifluoromethylanilines

Apparent dipole moments in benzene of a series of eight 4-substituted derivatives of NN-dimethyl-2-trifluoromethylaniline have been determined. Vector moments in the direction of the major axis of the ring have been calculated in order to explain the observed dipole moments. These vector moments are compared with corresponding values calculated for 4-substituted derivatives of NN-dimethylaniline. The influence of the 2-trifluoromethyl group on the extent to which para-substitution restores conjugation between the dimethylamino-group and the ring is noted.

A dipole moment study of alkylidenetriphenylphosphoranes, hexaphenylcarbodiphosphorane, phosphacumulene ylides and triphenylphosphazine

Analysis of the electric dipole moments in benzene of (dichloromethylene)triphenylphosphorane, hexaphenylcarbodiphosphorane, (2,2-diethoxyvinylidene)triphenylphosphorane and of benzoylmethylene- and p-nitrobenzoylmethylene-triphenylphosphoranes enables the Ph 3PCH 2 dipole moment to be estimated. The best value (4.5– 0.5 D) is derived from the dipole moments of (dichloromethylene)triphenylphosphorane and benzoylmethylenetriphenylphosphorane, which do not involve a hybridization moment of the ylidic carbon atom. This value corresponds approximately to the π-bond moment of the phosphorus—carbon bond of phosphorus ylides, and indicates that this π-bond has 55% ionic character. The mesomeric moments of the (PCCX) chain in triphenylphosphoranylideneketenes (Ph 3PCCX, with X  O, S or NPh) were derived and the values are briefly discussed. The dipole moment of triphenylphosphazine supports an E-conformation.

A dipole moment study of the ortho-effect in di- and tri-substituted NN-dimethylanilines

Apparent dipole moments in benzene of 2-methyl-, 2,3-, 2,4-, 2,5-, 2,6-, and 3,5-dimethyl-, 4-bromo-2,6-dimethyl, 2,6-dimethyl-4-nitro-, 2,4,6-timethyl-, and 2,4,6-tribromo-NN-dimethylaniline have been determined. Values for the magnitude and direction of the NN-dimethylaniline moment necessary to explain the dipole moments of six of these compounds are discussed in terms of the rotation of the dimethylamino-group from its position of maximum conjugation with the ring and the consequent change in vector moment in the direction of the major axis of the ring. The effect of p-substitution in restoring some conjugation between the dimethylamino-group and the ring is also noted.

Dipole moments of methyl- and trifluoromethyl-substituted methyl benzoates

Apparent dipole moments in benzene of 1,3-bistrifluoromethylbenzene and of the methyl esters of 2,4-dimethyl-,2,5-dimethyl-, 3,5-dimethyl-, 2,4-bistrifluoromethyl-, 2,5-bistrifluoromethyl-, 3,5-bistrifluoromethyl-, and 3-trifluoromethyl- benzoic acid have been determined. The values obtained can be explained either by rotation of the ester group out of the plane of the ring or, in the case of the 3-, and 2,4-substituted esters, by the existence of cis- and trans-isomers.

A dipole moment study of the ortho-effects of methyl and trifluoromethyl groups

Apparent dipole moments in benzene of the methyl esters of 2-methyl-, 2,6-dimethyl-, 2-trifluoromethyl-, and 2,6-bistrifluoromethyl-benzoic acid have been determined. The moments of the 2-substituted esters are explained by disturbance of the conjugation between the ester and phenyl groups (i) by the electronic effects of the ortho-groups and (ii) by a twisting of the ester group out of the plane of the benzene ring. The moments of the 2,6-disubstituted esters are independent of the angular displacement of the ester group and the important contribution of Ione-pair repulsions between the substituents in methyl 2,6-bistrifluoromethylbenzoate to the dipole moment is established.

A dipole moment study of the electrical effect of the trifluoromethyl group

Apparent dipole moments in benzene of a series of substituted trifluoromethylbenzenes and related compounds have been determined. The magnitude of the differences between the observed moments and those calculated by vector analysis are most appropriately explained, principally, in terms of a π electron inductive effect of the trifluoromethyl group.

Hydrogen bonding and substituent group effects in phénols. Part I. Apparent dipole moments and infrared spectra of N-(4-hydroxybenzylidene)-4-substituted-anilines in benzene, carbon tetrachloride, and dioxan

Apparent dipole moments in benzene and dioxan of benzylideneaniline and its two para-methyl derivatives have been determined, and used to obtain the inclination of the resultant moment to the N–C(ring) axis in each solvent. The moments in dioxan of 4-hydroxystilbene and 13 N-(4-hydroxybenzylidene)-4-substituted anilines are reported together with hydroxy-group stretching frequencies ν(OH) in carbon tetrachloride and dioxan. To explain the observed moments in dioxan, values of hydroxy-group bond moments µ(O–H) have been calculated. Both ν(OH) and µ(O–H) are found to be linearly related to the Hammett substituent constant, σ. The relative frequency shift in dioxan being adopted as a measure of the enthalpy change on solute–solvent association, these results provide another illustration of the dependence of µ(O–H) on the strength of hydrogen bonding.

Dipole moments and infrared spectra of a series of 4′-substituted 4-hydroxyazobenzenes

Apparent dipole moments in benzene and dioxan, and i.r. spectra of a series of 4′-substituted 4-hydroxyazobenzenes have been determined. The effect of the phenylazo-group is shown by comparing the moments with those of corresponding substituted phenols. The dipole moments determined in dioxan are all greater than those in benzene, indicating hydrogen bonding between the hydrogen atom of the hydroxyl group and the oxygen atom of the dioxan molecule. Calculations have been made of the O–H bond moments necessary to explain the observed moments in dioxan and µ(O–H) is found to be linearly related to Hammett's substituent constants, σ. Similar linear relationships are observed between the i.r. OH stretching frequency, ν(O–H), and σ. If the relative frequency shift in dioxan is a measure of the enthalpy change on solute–solvent association, then the dependence of O–H bond moment upon the strength of hydrogen bonding is demonstrated.

Conformations of some phenyl-substituted ethane derivatives as solutes

The electric dipole moments of 1,2-diphenyltetrachloroethane and of three 2,3-di-(p-halogenophenyl)2,3-di-methylbutanes have been measured in carbon tetrachloride at temperatures from –20 to 45°. Molar Kerr constants and dipole moments in benzene are also reported for these compounds as well as the related molecules 1,1,2,2-tetrachloroethane, 1,1,2,2-tetrabromoethane, p-bromocumene, p-fluorocumene, and 2,3-dimethyl-2,3-diphenylbutane. Conformational analysis of the results shows that substitution of two phenyl groups for the hydrogen atoms in tetrachloroethane has little effect on the relative stabilities of the rotational isomers in solution. Substitution of p-halogenophenyl groups for the two Cl or Br atoms in 2,3-dihalogeno-2,3-dimethylbutane reduces (a) the ΔE(solution) value almost to zero, thereby altering the gauche : trans isomeric ratio; and (b) the dihedral angle θ from about 70 to 65°.

Poly(ethylene oxide) in solution

AbstractMeasurements of the limiting viscosity number and dipole moments in benzene at 25°C. have been performed on carefully fractionated low molecular weight poly(ethyleneoxide) (M.W. ranging from 194 to 7770). The results of these measurements have been related to some hypotheses on the structure of molecules in the dissolved state. We have realized that internal rotations of the bonds are hindered by asymmetric potentials with a minimum near the gauche position. Although the exact shape of these potentials has not yet been defined, the so deduced conformation of the molecule in solution agrees very well not only with our measurements, but also with the most probable hypotheses obtained from x‐ray studies on crystalline structure and infrared spectra of POEG in various physical states.