Solvent Polarization Error and its Elimination in Calculating Dipole Moments

Halverstadt, I. F.; Kumler, W. D.

doi:10.1021/ja01264a078

Cited by 410 publications

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“…The instrument was not recalibrated but the measured dielectric constant of benzene (2.2726 to 2.2735) was in good agreement with that quoted (2.2730) in the previous work. The Halverstadt-Kumler equation (39) was used to obtain total molar polarizations, and electron polarizations were estimated from Vogel's values (40). No correction was made for atom polarization.…”

Section: Methodsmentioning

confidence: 99%

Kinetics and mechanism of electrophilic bromination of acetylenes

Pincock¹,

Yates²

1970

Can. J. Chem.

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The rates of addition of molecular bromine in acetic acid to a number of acetylenes have been found to follow the general equation In the absence of bromide ion and at low bromine concentrations (< 2 x M), only the k 2 process is observable. These k 2 values for a series of ring-substituted phenylacetylenes are correlated well with o+ values and give a p value of -5.17 which is interpreted in terms of a transition state leading to a vinyl cation intermediate. As expected from this intermediate, both cis and trans dibromide products are formed and the bromoacetates are only of the Markownikoff type (I-acetoxy-1-phenylethylene derivatives). An ion pair scheme has been presented to account for the variation in product composition with substrate structure.In contrast to these results for phenylacetylenes, a cyclic bromonium ion intermediate is postulated for alkyl acetylenes on the basis of only trans dibromide formation for 3-hexyne and 1-hexyne.The k,,-values have also been obtained for the ring-substituted phenylacetylenes as well as 3-hexyne. For all the substrates studied, this k,,-process represents a bromide ion catalyzed attack of molecular bromine in an Ade3 mechanism. Thus only trans dibromide products are formed from this rate process. The non-linear a + plot for these values has been interpreted in terms of change in transition state structure with substituent.Canadian Journal of Chemistry, 48, 3332 (1970) IntroductionAs recent reviews by de la Mare and Bolton (1) and Fahey (2) indicate, the electrophilic addition of bromine to acetylenes has received much less attention than the corresponding reaction with olefins. Furthermore, the results available are so incomplete and, in some cases contradictory, that little confidence can be placed in any of the postulated mechanisms. Thus, Robertson et al. (3) have suggested that the rate equation for the addition of bromine to several substituted acetylenes in acetic acid is similar to that observed for olefins (first order in substrate and both first and second order in bromine) and that the overall rates are in the expected order for an electrophilic process. In contrast, Sinn et al. (4) have measured rates for the brominatioii (by a process second order in bromine) of diphenylacetylenes in bromobenzene, that are best interpreted in terms of a nucleophilic reaction. Only slightly more information is available on the stereochemistry of the products of this addition reaction. Bergel'son and Nazarov (5) have reported that the addition of bromine to 3-hydroxypropyne, 3-hydroxy-3-methylbutyne, propyne, and acetylene gives exclusively trans addition under conditions that favor an ionic reaction. On the other hand, results for the bromination of diphenylacetylene by molecular bromine (6) and

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Section: Methodsmentioning

confidence: 99%

Kinetics and mechanism of electrophilic bromination of acetylenes

Pincock¹,

Yates²

1970

Can. J. Chem.

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“…Dielectric constants and specific volumes of either beilzene or (in one instance) dioxane solution were carried out as described previously (39,40) and calculations were made by the method of Halverstadt and Kumler (41). The distortion polarization was determined either from refractive index, additive refractions, or by direct determination with the solid substance (31).…”

Section: Electrical Polarization Studiesmentioning

confidence: 99%

The Stable Alkylation Products of Organonitrosohydroxylamines

George¹,

Kierstead²,

Wright³

1959

Can. J. Chem.

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The stable alkylation products of alkyl and aryl nitrosohydroxylan~ir~es seem to exist in a hitherto unknown structure, the diimide dioxide linkage. The alternative possibility is the alkyl diazotate monoxide structure, but the latter cannot account for the pure methane evolved when the substances are treated with methyl halide Grignard reagent. T h e principal products of this reaction with Grignard reagents are diirnide monoxides formed subsequently by addition of an equivalent of reagent with elimination of the original alkoxy group a s its magnesium salt. Nitration of N-methyl-N'-phenyldiimide dioxide shows that in salt-forming media (nitric-sulphuric) the NpOzR group is electrically negative, but dipole moment studies show that it is highly degenerate. This resonance stabilization is not ~~nexpected in view of the high stability of the diimide dioxides in acidic media.The first i~itrosohydroxylamii~es were prepared (1) by reaction of nitric oxide with substances contailling an active methylene group in presence of ethanolic sodium hydroxide. Typical is the reaction with acetone which may be postulated as follows:The second, more orthodox, method of preparation involved the nitrosation of a n arylhydroxylamine (2), and led to the preparation of salts such as ammonium phenyl~~itrosohydroxylaminate (cupferron). The free acids are rather unstable.When the silver salts of these nitrosohydroxylamines (11, NI = Ag) are treated with alkyl iodides two products, designated a and P, are formed. The P isomers may be desig-,hT=O N=O Me1 R-N

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“…The higher values probably can be attributed to small experimental errors in measuring the dielectric constant of the solvent or of the more dilute solutions. Such errors have a disproportionately large effect on the polarization at infinite dilution when obtained by the conventional extrapolation [10].…”

Section: Dipole Moments Of Picratesmentioning

confidence: 99%

Dipole moments and molecular association of some picrates of primary, secondary, and tertiary amines in benzene and dioxane

Maryott¹

1948

J. RES. NATL. BUR. STAN.

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The dielectric constants of dilute benzene and dioxane solutions of primary, secondar y, and tertiary amine salts of picric acid were measured . Dipole moments are reported fo r the picrates of t h e followingamines ; in benzene: tri-iso-a m yl-(11.9), tTi-n-b uty l-(11.9) , t ri ethyl· (11.7) , di ethylben zyl-(11 .8) , di-n-butyl-(11.5) , di-n-p ropyl-(11. 5) ; in d ioxanc : tr·i-n-butyl-(12.2) , di-n-butyl-(12.1) , n-ocLy l-(12.1), and n-octadecyl-(12.3). The picrates of primary and secondary amincs show a p rono un ced t endency to a s ociate in benzene, as cvidenced by the nonlincar variation in die lectri c constan t with concentration , but not in d ioxane . The efrect of the s ize a nd shape o f th e a lk y lammo nium ion and of hydrogen bo ndin g on t he a ssociation a re d iscusscd .

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Solvent Polarization Error and its Elimination in Calculating Dipole Moments

Cited by 410 publications

References 0 publications

Kinetics and mechanism of electrophilic bromination of acetylenes

Kinetics and mechanism of electrophilic bromination of acetylenes

The Stable Alkylation Products of Organonitrosohydroxylamines

Dipole moments and molecular association of some picrates of primary, secondary, and tertiary amines in benzene and dioxane

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