The Dipole Moment and Structure of Urea and Thiourea<sup>1</sup>

Kumler, W. D.; Fohlen, G. M.

doi:10.1021/ja01260a054

Cited by 115 publications

(42 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The value for thiourea [5.4(2.5) debye; 1 debye = 3.34 x 10 -30 C m], agrees satisfactorily with the value 4.86 debye obtained for thiourea in dioxane solution (Kumler & Fohlen, 1942 He, Swaminathan, Craven & McMullan, 1986]. The molecular dipole moments in TUPA are in directions close to the bonds S~ C in thiourea and C(2)~ 0(2) in parabanic acid (see Fig.…”

Section: ( B ) Electrostatic Propertiessupporting

confidence: 80%

Structure and charge density of the 1:1 complex of thiourea with parabanic acid at 298 K

Weber¹,

Craven²

1987

Acta Crystallogr Sect B

View full text Add to dashboard Cite

Even though the calculated values for the lattice energy could not be directly compared with the experimental ones because of the limitations of the approach used, it can be illustrative to compare the values obtained in the different runs when the hydrogen bonds are omitted. When the electrostatic term is not included, values of the lattice energy for rigid molecules (no subrotations) are in the range 70-100 kJ mol -~, whereas when molecular subrotations are relaxed lattice-energy values are in the range 100-160 kJ mo1-1. For runs including the electrostatic term, the lattice energy is in the range 100-170 kJ mol -~ when rigid molecules are considered and 130-200kJ mol -~ when molecular subrotations are relaxed. So, an unexpectedly large Coulombic contribution to the lattice energy, ranging from 30 to 60% of the total estimated lattice energy, is found. In our opinion, this high contribution is a qualitatively significant feature, in spite of the approach and the potential parameters used and the method of estimating effective atomic charges. Generally, it was tacitly assumed that the Coulombic contribution to the lattice energy is negligible but some previous results indicate that this assumption is not valid in all hydrocarbon crystals, reaching a value of 29% of the total lattice energy of benzene and up to 59% in other cases (Williams & Cox, 1984).If the Coulombic contribution to the lattice energy seems to be significant for these crystals, it is true, however, that the inclusion of the electrostatic term does not significantly affect the values of the optimized structural parameters. The overall fit between the theoretical configuration and experimental structure is, in general, slightly more satisfactory for runs including the electrostatic contribution, but conclusive general results on the effects of its inclusion on molecular rotation and translation would be difficult to establish.Within the limits of the approach and the potential functions used, we think that the reported results clearly indicate that the electrostatic term makes an important contribution to the lattice energy of these compounds but has little effect on the optimized structural parameters. A major limitation for accuracy in these calculations, in our opinion, is the description of the hydrogen bonds, but further improvements should be possible by defining a realistic potential function for these interactions.

show abstract

Section: ( B ) Electrostatic Propertiessupporting

confidence: 80%

Structure and charge density of the 1:1 complex of thiourea with parabanic acid at 298 K

Weber¹,

Craven²

1987

Acta Crystallogr Sect B

View full text Add to dashboard Cite

show abstract

“…Concerning these two molecules, the hydrogen-bonding ability of amino groups is hindered and only the carbonyl-water interactions can be considered. A possible explanation is that the C=O-water interactions are the most important and that they are maximal when the dipole moment is the greatest (1,3-dimethylurea larger than tetramethylurea (48,49)). …”

Section: Experimental and Resultsmentioning

confidence: 99%

Apparent Molal Volumes and Heat Capacities of Urea and Methyl-Substituted Ureas in H₂O and D₂O at 25 °C

Philip¹,

Perron²,

Desnoyers³

1974

Can. J. Chem.

View full text Add to dashboard Cite

The apparent molal volumes and heat capacities of urea, 1,l-and 1,3-dimethylurea, and tetramethylurea were measured in H?O and DL.O at 25 " C . From these data, ureawater interactions seem to cause an overall structure-breaking effect and the substituted ureas, an overall structure-making effect. The effect of the hydrogen-bonding interactions to the volume and heat capacity seems to be small compared with the intrinsic and hydrophobic contributions of a methylene group, as reflected by the isotope effect.

show abstract

“…Using the measured dipole moment of thiourea in a dioxane solution, 4.86 debyes (Kumler & Fohlen, 1942), our hydrogenous low temperature structure gives a spontaneous polarization of 2.3_+0.1 /~C.cm -1 compared with the observed value 3.2_+0.1 /zC.cm -I. Using the ionic model suggested by Calvo, in which each sulphur atom has a charge of 0.42 electron and each nitrogen has -0.2l electron, we made preliminary calculations of the electric fields at the atom sites, using the Ewald transformation (Ewald, 1921), and obtained an average value of 0.11 × 106 esu.cm -2 for the field along the C-S bond.…”

Section: Ferroelectricity In Thioureamentioning

confidence: 99%

A neutron diffraction determination of the crystal structures of thiourea and deuterated thiourea above and below the ferroelectric transition

Elcombe¹,

Taylor²

1968

Acta Cryst Sect A

156

View full text Add to dashboard Cite

410 THE CORRECTION OF MEASURED INTEGRATED BRAGG INTENSITIES 0( 4 is the corresponding value calculated for the finite aperture (0-20 scan) and it can be seen that the approximation of an intinite slit in this case gives an error of the order of 300/0 in the TDS contribution to the peak scan. The values obtained for a spherical volume (~5) are in this case also quite good approximations for 0 > 40 °; the effective scan range being + 1-47 °. A sphere of equal volume would give an effective scan range of + 1.43 ° resulting in values of 7 30/0 lower than ~5. These effective scala ranges may be compared with the true scan range of + 1.2 °; a spherical volume using the true scan range would thus give values of c~ of the order of 20% too small in this case. The error in the intensities resulting from ignoring the TDS correction would again be less than about 1% with a corresponding error in the mean temperature factor. The relative agreement between the various ~ values is also illustrated in Fig. 2.We have also estimated the 'mosaic spread' effect for the barium fluoride measurements. The full width at half height of the mcasured peaks varied from 0.2 ° up to 0.8 ° resulting in a reduction of the TDS correction between 1% and 10%. This can therefore be an important factor particularly if the width of the measured peaks changes rapidly with the scattering angle and passes through a focusing position. The structures of thiourea, SC(NH2)~,, and deuterated thiourea, SC(ND2)2, have been determined at room and liquid nitrogen temperatures from three-dimensional neutron diffraction data. No significant structural change on deuteration has been found. N-H.--S hydrogen bonds occur in both materials at both temperatures with N-S distances of 3.35-3-43/~ and N-H-S angles of 169-171 ° and, apart from these hydrogen atoms, the molecules are planar to within 0-010/~. An analysis of the thermal parameters of the atoms in each molecule in terms of rigid vibration parameters shows that at liquid nitrogen temperature the molecules are fairly rigid whereas at room temperature there are serious deviations from rigidity. Excellent agreement has been found between the thermal vibrations of the molecules at room temperature and the observed structure change to the lower ferroelectric state. A qualitative theory of the fcrroelectric nature of thiourea is proposed which explains the observed temperature variation of the spontaneous polarization and coercive field in the lower ferroelectric region, in terms of a variable molecular orientation and a single hydrogen bond which is switched from one sublattice to the other during ferroelectric reversal.

show abstract

The Dipole Moment and Structure of Urea and Thiourea¹

Abstract: The only work in the literature on the dipole moment of urea is that of Bergmann and Weizmann,2 who obtained a value of 8.6 in dioxane. A redetermination of the moment of this very important compound seems desirable for several reasons.

Cited by 115 publications

References 0 publications

Structure and charge density of the 1:1 complex of thiourea with parabanic acid at 298 K

Structure and charge density of the 1:1 complex of thiourea with parabanic acid at 298 K

Apparent Molal Volumes and Heat Capacities of Urea and Methyl-Substituted Ureas in H₂O and D₂O at 25 °C

A neutron diffraction determination of the crystal structures of thiourea and deuterated thiourea above and below the ferroelectric transition

Contact Info

Product

Resources

About

The Dipole Moment and Structure of Urea and Thiourea1

Abstract: The only work in the literature on the dipole moment of urea is that of Bergmann and Weizmann,2 who obtained a value of 8.6 in dioxane. A redetermination of the moment of this very important compound seems desirable for several reasons.

Cited by 115 publications

References 0 publications

Structure and charge density of the 1:1 complex of thiourea with parabanic acid at 298 K

Structure and charge density of the 1:1 complex of thiourea with parabanic acid at 298 K

Apparent Molal Volumes and Heat Capacities of Urea and Methyl-Substituted Ureas in H2O and D2O at 25 °C

A neutron diffraction determination of the crystal structures of thiourea and deuterated thiourea above and below the ferroelectric transition

Contact Info

Product

Resources

About

The Dipole Moment and Structure of Urea and Thiourea¹

Apparent Molal Volumes and Heat Capacities of Urea and Methyl-Substituted Ureas in H₂O and D₂O at 25 °C