摘要:

The densities and heat capacities per unit volume of the symmetrical tetraalkylammonium bromides (R4NBr) were measured in H2O, D2O, and 3 maqueous urea from 0.01 to 1 mol kg−1and from 5 to 55 °C with a flow digital densimeter and a flow microcalorimeter. Expansibilities were also measured at 25 °C for the same electrolytes in H2O and urea–water mixtures with a dilatometer. Apparent molal volumesheat capacitiesand expansibilitieswere derived. Theof R4NCl and R4NI were also measured in H2O at 25 °C. The effect of urea concentration was investigated at 25 °C in the case of Bu4NBr.Once allowance is made for the anion, the properties of the larger R4N+behave essentially as hydrophobic nonelectrolytes in water. The transfer functions from H2O to D2O have the same sign as the hydration functions and the transfer functions from H2O to urea–water mixtures the opposite sign. Whatever is the origin of the interactions giving rise to the peculiar behavior of hydrophobic R4N+in water, these interactions are larger in D2O and smaller in the presence of urea.The excess volumes, heat capacities, and expansibilities of Bu4NBr and Pen4NBr, once corrected for the long-range Debye–Hückel interactions, all have the same sign as the hydration functions at infinite dilution, in contrast with excess free energies and enthalpies. This suggests some kind of cooperative effect as two hydrophobic solutes interact with each other without the formation of a hydrophobic bond. No conclusions can be drawn from the difference in excess functions in the various aqueous solvents.

ISSN:0008-4042    

DOI:10.1139/v76-309

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Trimethyltin hypophosphite, Me3SnPO2H2, bis(trimethyltin) phosphite dihydrate, (Me3Sn)2PO3H.2H2O, and bis(triphenyltin) phosphite, (Ph3Sn)2PO3H, have been obtained from the organotin chloride and aqueous solutions of the sodium salt of the corresponding phosphorus oxy-acid. (Me3Sn)2PO3H.2H2O can be dehydrated under vacuum at 25 °C, but disproportionation occurs on heating. Tris(trimethyltin) orthophosphate, (Me3Sn)3PO4, was prepared from trimethyltin chloride and silver phosphate in methanol and gave an adduct formulated asafter recrystallization from 1,4-dioxane. Vibrational spectra and Mössbauer data for Me3SnPO2H2are consistent with a trigonal bipyramidal structure in which planar Me3Sn groups are bridged symmetrically by PO2H2groups. The Mössbauer spectra of (Me3Sn)2PO3H, (Ph3Sn)2PO3H, and (Me3Sn)2PO3H.2H2O suggest that the two tin atoms are in similar (probably pentacoordinate) environments, implying at least one three coordinate oxygen per formula unit. For (Me3Sn)3PO4, the vibrational spectra, Mössbauer data, and physical properties are consistent with a weakly associated structure in which all three tin atoms are in similar environments. It is suggested that association is achieved via the phosphoryl (P=O) oxygen atom, which is weakly coordinated to three tin atoms leading to a distortion of the tetrahedral arrangement around tin towards trigonal bipyramidal.

ISSN:0008-4042    

DOI:10.1139/v76-310

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The influence of neutral salts on the easily polarizable hydrogen bond of H5O2+groupings in aqueous acid solutions is studied, using ir spectroscopy. The absorbance of the ir continuum, caused by the polarizable hydrogen bond in the H5O2+groupings, usually decreases with increasing neutral salt concentration. This is explained by the polarization of the hydrogen bonds caused by local fields due to the neutral salt ions. The H+becomes more or less trapped at one of the H2O of the H5O2+. The prominence of this effect increases with increasing cation field,i.e., from Cs+to Li+, and is more pronounced with bivalent than with monovalent cations. The opposite effect is observed with tetraethylammonium chloride. The symmetry of H5O2+groups is less strongly disturbed in the presence of neutral salts with ions with very large radii,i.e., small electrical fields, than in pure acid solutions. Considering the torsional vibration of the water molecules, it is finally shown that the hydrate structure network around the H5O2+becomes disintegrated due to the presence of neutral salts.It is known from electrochemical investigations that the activity coefficient of the excess proton usually increases strongly due to the addition of neutral salts to acid solutions. The opposite is true with the addition of tetraethylammonium salt. Furthermore, the addition of neutral salt decreases the excess proton conductivity. All these observations are discussed on the basis of the ir spectroscopic results.

ISSN:0008-4042    

DOI:10.1139/v76-311

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The hydration of norbornadiene (1) under the HTDA conditions of aqueous acetic acid at 250 °C gives via norbornanediols and norbornenols as intermediates, the sink-product aldehydes3, 4, 5, and norcamphor (6). When the reaction is carried out in deuterated medium on the average, 2.5 atoms of deuterium are incorporated into each of the products. Hydration of benzonorbornadiene (2) at 250 °C gives the alcohols40and41and the acetates42aand42bas products. When the hydration is carried out in deuterated medium, while only one atom of deuterium is incorporated into the [2.2.1]-framework, exchange of the aromatic moiety proceeds to completion.

ISSN:0008-4042    

DOI:10.1139/v76-312

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The hydration of norbornene (1) and nortricyclane (2) under the high temperature and dilute acid (HTDA) conditions of aqueous acetic acid at 250 °C gives as productsexo-2-norborneol,endo-2-norborneol,exo-2- andendo-2-norbornyl acetate, and a mixture of stereoisomeric dinorbornyl ethers4. When the reactions are carried out in deuterated medium perdeuteration (>90% in one cycle) of the [2.2.1]-products is accomplished. Respectable overall yields (50–70%) of the products are obtained. Solvolysis of the productsexo-norborneol, andendo-norbornyl acetate under HTDA(D) conditions also leads to perdeuterated3a,3b,3c,3d, and4.

ISSN:0008-4042    

DOI:10.1139/v76-313

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Infrared and Raman spectra of 1,2-dibromotetrafluoroethane have been recorded in vapour, liquid, and polycrystalline solid states. Assignments have been made totransandgaucheisomers. A force field has been obtained for thetransisomer and used to predict the frequencies of thegaucheform.

ISSN:0008-4042    

DOI:10.1139/v76-314

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The conformational preferences in CCl4solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between twoorthobromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

ISSN:0008-4042    

DOI:10.1139/v76-315

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The doubly hydrogen bonded conformation of 2,2′-dihydroxy-4-methoxybenzophenone ensures substantial nonbonded interactions between C—H bonds on neighbouring aromatic rings and gives rise to spin–spin coupling between the protons in those bonds. Because of the relative orientation of the C—H bonds containing the coupled protons, the coupling represents a direct mechanism which probably does not depend on the orbitals of the carbon atom. The observed coupling between the hydroxyl protons, formally over eight bonds, is small and indicative of an inappreciable covalent character of the hydrogen bond, in agreement with recent conclusions that a weak hydrogen bond is best represented by electrostatic and non-bonded forces only.

ISSN:0008-4042    

DOI:10.1139/v76-316

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The signs and magnitudes of spin–spin coupling constants over five and/or six bonds in someN-methyl andN,N-dimethyl hydrazones, in methyl vinyl ether, 4-methoxy-3-butene-2-one, 1-methoxy-1,3-butadiene, 1-butene, and in anisole are discussed in terms of coupling mechanisms. In the hydrazones the five-bond couplings between methyl and olefinic protons are negative, while six-bond couplings between protons in methyl groups are positive, a reversal of the expected sign sequence. INDO-MO-FPT calculations are not in agreement with observation, but the disagreement may be a consequence of faulty structural assumptions. The sizeable six-bond couplings imply a negative σ–π contribution to the five-bond constants. The calculated and observed negative couplings over five bonds in methyl vinyl ether and the other molecules above emphasize their dependence on the proximity of the bonds containing the coupled nuclei and are reliable indicators of bond arrangements in these molecules.

ISSN:0008-4042    

DOI:10.1139/v76-317

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The long-range spin–spin coupling constants between hydroxyl protons and ring protons or fluorine nuclei are used to establish the conformer populations in iodine and brornine derivatives of 2-trifluoromethylphenol in C6H12, CCl4, and C6D6solutions. The sequence Cl,is established for the so-called hydrogen bonding preferences of the hydroxyl group in 2,4,6-trisubstituted phenols, the corresponding free energy sequence being −ΔG = 1690, 1690 > 1300 > 1230 > 0 ± 200 cal/mol at 32 °C in CCl4solution. An indirect estimate of the free energy differences in the vapor phase suggests the sequence −ΔG = 2800, 2800 > 2400 > 2300 > 1100 ± 300 cal/mol; the latter value meaning that the hydroxyl group in 4-bromo-2-trifluoromethylphenol prefers the CF3group by this amount in the vapor phase. Benzene interacts preferentially with the OH group in this compound to the extent of 1300 cal/mol (ΔG), referenced to the vapor phase.

ISSN:0008-4042    

DOI:10.1139/v76-318

出版商:NRC Research Press    

年代:1976

数据来源: NRC