The heat of formation of liquid methanesulfonic acid, -178.09 ± 1.48, was determined by measuring the heat of reaction of methyl thiolacetate with aqueous hypochlorite solution to give aqueous methanesulfonate and acetate. The heats of formation of liquid methanesulfonyl chloride, -126.91 ± 1.54, and methyl methanesulfonate, -164.34 ± 1.58, were determined by measuring the heats of reaction of methanesulfonyl chloride with water or methanol in the presence of a suitable basic catalyst. Heats of vaporization (based on vapor-pressure data), entropies (based on ab initio molecular orbital calculations), and free energies of transfer from gas phase to aqueous solution were calculated leading to values for the free energies of formation in aqueous solution. The free energies of formation so determined were methanesulfonic acid, -151.72 ± 2.68, methanesulfonyl chloride, -101.29 ± 1.96, and methyl methanesulfonate, -127.28 ± 2.08. From these values the free energies of hydrolysis (leading to unionized methanesulfonic acid) are methanesulfonyl chloride, -25.11 ± 3.04, and methyl methanesulfonate, -9.90 ± 2.48.Key words: sulfonic acids, heat of formation, free energy of formation, hydrolysis.

While deuterium kinetic isotope effects for solvolyses have been extensively studied, other nucleophilic substitutions have received less attention, and identity processes, that is, substitutions where the nucleophile and leaving group are the same, have rarely been examined. Identity reactions must pass through a truly symmetrical stage, a transition state or an intermediate, so that data will be of interest to both theoretical and experimental chemists. Values of kH/kD have been determined by polarimetry for bromide exchange– racemization at ArCHBrCH3/CD3 (Ar = C6H5,4-Br- and 4-Me-C6H4, and 3,4,-dimethyl-C6H3) in acetone, acetonitrile, and nitromethane. Observed values are analogous to values seen in solvolyses. They range from 1.01 to 1.35 and, in some cases, increase markedly as the concentration of Bu4NBr decreases. Solvolyses are either first order or pseudo first order whereas plotting observed racemization rate versus [Bu4NBr] allows separation of first- and second-order components; those species giving more stable carbocations in the more dipolar solvents, the systems showing kH/kD variation with Br− concentration, alone show an appreciable first-order component. The second-order kH/kD ratio averages 1.062 ± −0.018 at temperatures ranging from 25 to 50 °C for all substrates in the three solvents, very analogous to the values seen for racemization of 1,1,1-d3-2-bromooctane or solvolysis of ethyl substrates but considerably lower than the typical solvolysis values of 1.15–1.25 for secondary, and 1.35–1.5 for tertiary substrates. The first-order kH/kD values obtained are higher, 1.1–1.5. These and other results are discussed.

No, or at most very small, salt effects have been detected for second-order racemizations of various 1-phenylbromoethanes, confirming that the "mixed kinetics", previously reported for 4-methyl- and 3,4-dimethylphenylbromoethanes with tetrabutylammonium bromide in acetonitrile and nitromethane, did not reflect a salt effect on a unimolecular reaction. Thus the uni- and bimolecular rate components can be evaluated using the equation:[Formula: see text]where k1 = first-order or unimolecular rate constant, the intercept, and [Formula: see text], the latter being the rate constant for the bimolecular substitution. A "special salt effect" was found for the unimolecular component; it was especially pronounced for 3,4-dimethyl substrate in acetonitrile with Bu4NClO4 as the electrolyte. In acetone, where no unimolecular reaction component was detected even with those substrates giving the most stable carbocations, the only salt effect was a common ion, Bu4N+, effect on the incomplete dissociation of Bu4NBr. From an iterative best fit for plots of observed rate versus calculated bromide ion activity for unsubstituted, 4-methyl, and 3,4-dimethyl substrates, Kassoc ~ 15 ± 1 at 40 °C. The results are interpreted as additional support for a progression of mechanism with nucleophilic attack possible at any stage of the series of equilibria: substrate [Formula: see text] contact ion pair [Formula: see text] various solvated ion pairs [Formula: see text] dissociated ions. Keywords: special salt effects, ionic strength effects, racemization of 1-phenylbromoethanes, mechanism of nucleophilic substitution, ion pair mechanism.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOn the mechanism of reduction by reduced nicotinamide adenine dinucleotide dependent alcohol dehydrogenase. .alpha.-Halo ketones as mechanistic probesDennis D. Tanner and A. R. SteinCite this: J. Org. Chem. 1988, 53, 8, 1642–1646Publication Date (Print):April 1, 1988Publication History Published online1 May 2002Published inissue 1 April 1988https://pubs.acs.org/doi/10.1021/jo00243a009https://doi.org/10.1021/jo00243a009research-articleACS PublicationsRequest reuse permissionsArticle Views315Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe mechanism of the reduction of .alpha.-halo ketones by several models for NADH. Reduction by a SET-hydrogen atom abstraction chain reactionDennis D. Tanner, Harrbansh Kumar Singh, Abdelmajid Kharrat, and Allan R. SteinCite this: J. Org. Chem. 1987, 52, 11, 2142–2146Publication Date (Print):May 1, 1987Publication History Published online1 May 2002Published inissue 1 May 1987https://pubs.acs.org/doi/10.1021/jo00387a005https://doi.org/10.1021/jo00387a005research-articleACS PublicationsRequest reuse permissionsArticle Views554Altmetric-Citations32LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Kinetic chlorine isotope effects attending the solvolysis of several ring-substituted 1-phenylethyl chlorides in alcohol–water solvent mixtures are reported. The k35/k37 values are insensitive to the identity of ring substituents and to solvent composition. Results are interpreted in terms of an SN1 heterolytic process incorporating a significant amount of internal return. Theoretical calculations suggest that the incipient chloride ion in the transition state may be strongly hydrogen-bonded.

Results of kinetic studies of the racemizations and radio-bromide exchanges with 1 -arylbromoethanes in acetone with added LiBr are reported. The results are direct empirical evidence supporting the ion-pair mechanism for bimolecular nucleophilic displacement at saturated carbon. For the unsubstituted and less electron rich substrates, behaviour expected for a classical Sn2 mechanism is found, but for 1-(4-methylphenyl)bromoethane, the racemization rate is greater than twice the exchange rate, indicating internal return with racemization from a solvated ion pair. For 1-(3,4-dimethylphenyl)bromoethane, the carbocation is sufficiently stabilized that the reaction shows intermediate behaviour; the racemization rate is significantly less than twice the exchange rate, for example. Through the series from the electron withdrawer to electron donor substituted substrate, the activation parameter ΔH≠ progressively decreases and ΔS≠ becomes rapidly more negative.

A fast, convenient procedure for preparing and resolving moderate to large quantities of chiral secondary alcohols is described. The general procedure involves a one-pot conversion of the ketone (various acetophenones) to the half-ester of a diacid (succinic, phthalic… ) and resolution with (+)- and (−)-1-phenylethylamines. Overall yields of the enantiomeric alcohols, the variously substituted 1-phenylethanols, are generally 65–85% with optical purities of approximately 90%. Properties and optical rotations of a number of chiral 1-phenylethanols and of the bromides made from them are tabulated. A discussion of optical purity determinations using nmr methods is included and absolute configurations are reported.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNonlinearity of Hammett .sigma..rho. correlations for benzylic systems: activation parameters and their mechanistic implicationsAllan R. Stein, Michal Tencer, Elizabeth A. Moffatt, Robert Dawe, and James SweetCite this: J. Org. Chem. 1980, 45, 17, 3539–3540Publication Date (Print):August 1, 1980Publication History Published online1 May 2002Published inissue 1 August 1980https://pubs.acs.org/doi/10.1021/jo01305a045https://doi.org/10.1021/jo01305a045research-articleACS PublicationsRequest reuse permissionsArticle Views575Altmetric-Citations18LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

The method reported allows the simultaneous determination of relative and absolute rate constants for two substances in a single kinetic run. The approach is of special interest for kinetic isotope effect determinations where rate ratios are often near one and failure to exactly duplicate reaction conditions can lead to uncertainties in the values calculated from independently measured rate constants. For racemization studies, using two optically active materials with opposite signs of rotation, knowing their initial rotational contribution and having the faster racemizing one in higher concentration, the rates can be calculated if the times required to reach zero net rotation and the extremum value are measured. Other systems to which the method can be extended are suggested.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRacemization and bromide exchange studies on 1-phenylbromoethane and the question of the ion-pair mechanism for bimolecular nucleophilic substitutions at saturated carbonAllan R. SteinCite this: J. Org. Chem. 1976, 41, 3, 519–523Publication Date (Print):February 1, 1976Publication History Published online1 May 2002Published inissue 1 February 1976https://pubs.acs.org/doi/10.1021/jo00865a023https://doi.org/10.1021/jo00865a023research-articleACS PublicationsRequest reuse permissionsArticle Views117Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFallacious separation of uni and bimolecular reactionsAllan R. Stein Cite this: J. Chem. Educ. 1975, 52, 5, 303Publication Date (Print):May 1, 1975Publication History Received3 August 2009Published online1 May 1975Published inissue 1 May 1975https://doi.org/10.1021/ed052p303Request reuse permissionsArticle Views72Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alertsclose Get e-Alerts

AbstractDie vielstündige‐mehrtägige Alkylierung der Alkalimetall‐ oder Tetraäthylammoniumsalze der Anilide (II) z.B. mit Benzylbromid ergibt in DMF ausschließlich die N‐ 1A alkylierten Produkte (I).

Systematic studies of the alkylation of a number of ambident or ambifunctional anions have been reported. For the vast majority of the anions examined reaction involved competition between carbon and a heteroatom and few competition between two heteroatoms. A study of the factors influencing the site of alkylation of the ambident anion of mono-N-substituted amides, where competition is between oxygen and nitrogen, has been undertaken. With the alkali metal and tetraalkylammonium salts of formanilide anions, the alkylation product is invariably the corresponding N-alkylformanilide. No detectable O-alkylation is observed as the solvent is varied from nonpolar through polar aprotic solvents, the alkylating agent through the various benzyl halides and para-substituted benzyl halides and the para-substituent on the formanilide from strongly electron donating (—OCH3) through strongly electron withdrawing (—NO2) groups. In contrast, with the silver formanilide salts, O-alkylation predominates but here the O:N alkylation ratio varies with the parameters examined. A rationale based on thermodynamic υs. kinetic control and reaction of dissociated υs. undissociated anion is presented to predict the site of reaction in these and other ambident systems.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReexamination of the racemization of 1-phenylbromoethane in acetoneAllan R. SteinCite this: J. Org. Chem. 1973, 38, 23, 4022–4026Publication Date (Print):November 1, 1973Publication History Published online1 May 2002Published inissue 1 November 1973https://pubs.acs.org/doi/10.1021/jo00987a014https://doi.org/10.1021/jo00987a014research-articleACS PublicationsRequest reuse permissionsArticle Views42Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

The generally accepted hypothesis that the alkylation of metal phenoxides is forced to occur at the ortho-carbon in heterogeneous reactions was investigated. Methyl iodide and bromide vapor reacts with crystalline sodium and lithium 2,6-dimethylphenoxides to give ortho-carbon/oxygen alkylation ratios not unlike those obtained in sealed tube reactions with an excess of methyl iodide or with added toluene as solvent. However, an unprecedented amount of para-methylation also occurred. The implications of these and related observations in other systems are discussed.

The alkylation of the di-alkali metal salts of resorcinol with methyl iodide under various conditions was examined. Solvent and cation effects on the mode and position of resorcinolate anion methylation are discussed. By examination of the neutral and phenolic fractions and comparison with the alkylation of methoxyphenols and mesorcinol, the principal methylation sequences are determined. The intermediacy of the various hydroxydienones, for example, 2,4,6,6-tetra-and 2,6,6-tri-methyl-1-hydroxycyclohexa-1,4-dien-3-one, in the formation of the principal product, 2,2,4,6,6-pentamethylcyclohex-4-en-1,3-dione, from the methylation of the resorcinolate dianion in nonpolar solvents or water is established by the isolation of such intermediates. The 2,2,4,6,6-pentamethylcyclohex-4-en-1,3-dione itself will be discussed in detail in the second paper in this series.