1-adamantyl Chloride Research Articles

Fluorine/adamantane modified cyanate resins with wonderful interfacial bonding strength with PBO fibers

Novel compound (AEAF) with both cage-type adamantanes and fluorine-containing structures was synthesized from bisphenol AF, 1-adamantyl chloride and epichlorohydrin through successive esterification and O-alkylation reaction, which was then introduced into the curing networks of bisphenol A cyanate ester (BADCy) resins through copolymerization, to obtain AEAF-co-BADCy resins. AEAF presented low polarizability & dipole density, rigid cage adamantane, and stable CF3 group. When the mass fraction of AEAF was 6 wt%, AEAF-co-BADCy resins displayed the minimum real part (ε′r), imaginary part (ε”r) of complex permittivity, and dielectric loss tangent (tanδ) values, which were 2.49, 0.012, and 0.0048, respectively. And the corresponding wave transmission efficiency (T) was 92.3%, significantly higher than that of pure BADCy (86.6%). AEAF-co-BADCy resins also possessed excellent mechanical properties and better interfacial compatibilities with poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers. The corresponding flexural strength (126.5 MPa) and impact strength (15.2 kJ m−2) were increased by 16.6% and 47.6%, in comparison to pure BADCy (flexural strength of 108.5 MPa and impact strength of 10.3 kJ m−2). Meantime, the single fiber pull-out strength of PBO fibers/AEAF-co-BADCy (6 wt% AEAF) micro-composites also displayed an increase from 3.1 MPa (PBO fibers/BADCy) to 3.4 MPa.

Detailed Analysis for the Solvolysis of Isopropenyl Chloroformate.

The specific rates of solvolysis (including those obtained from the literature) of isopropenyl chloroformate (1) are analyzed using the extended Grunwald-Winstein equation, involving the N(T) scale of solvent nucleophilicity (S-methyldibenzothiophenium ion) combined with a Y(Cl) scale based on 1-adamantyl chloride solvolysis. A similarity model approach, using phenyl chloroformate solvolyses for comparison, indicated a dominant bimolecular carbonyl-addition mechanism for the solvolyses of 1 in all solvents except 97% 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). An extensive evaluation of the outcomes acquired through the application of the extended Grunwald-Winstein equation resulted in the proposal of an addition-elimination mechanism dominating in most of the solvents, but in 97-70% HFIP, and 97% 2,2,2-trifluoroethanol (TFE), it is proposed that a superimposed unimolecular (S(N)1) type ionization is making a significant contribution.

Solvent distributions, solvent orientations and specific hydration regions around 1-adamantyl chloride and adamantane in aqueous solution

Ab initio molecular orbital theory and Monte Carlo method with molecular mechanics are used to calculate the hydration numbers and solvent configurations around 1-adamantyl chloride in 324 water molecules. In the highest probability region for distribution of water molecules, a water molecule forms two hydrogen bonds with Cl and the adamantane skeleton; in the second highest probability region, a water molecule is located at the rear side. The CH⋯O interaction in the rear side is enhanced by the Cl substitution. The water orientation in the rear side of 1-adamantyl chloride is different from that around a hydrophobic adamantane molecule.

Enantioresolution and Chameleonic Mimicry of 2-Butanol with an Adamantylacetyl Derivative of Cholic Acid

[3β,5β,7α,12α]-3[(Adamantyl-1-acetyl)-amino]-7-12-dihydroxycholan-24-oic acid (AdCH2CA) was synthesized by the reaction between 1-adamantyl acetyl chloride and the methyl ester of 3β-amino-cholic acid and hydrolysis of the ester. The acid was recrystallized from racemic 2-butanol (0.1% water). Crystals are orthorhombic (P212121) and form inclusion complexes with water and 2-butanol with a 1:1:1 stoichiometry. Only the S-enantiomer is included into the structure of the crystal, exhibiting a chameleonic mimicry with the steroid bilayers. The isolation of crystals allows the enantioresolution of the racemate with a high purity (≈99%) of S-2-butanol. The steroid molecules are disposed in an antiparallel orientation in the hydrophobic layer and a parallel orientation in the hydrophilic one.

Elucidation of Concentrated Salt Effects on the Solvolysis Reactions of Typical SN1 and SN2 Substrates in Sulfolane–Water Mixed Solvent

Abstract In a 50 vol % sulfolane–H2O mixed solvent, extensive studies have been carried out of the concentrated salt effects on the solvolysis reaction rates of aliphatic halides and related compounds (RX). In the solvent system, the “pseudo” first-order rate constants (k/s−1) of typical SN1 substrates, 1-adamantyl chloride and bromide, or 2-adamantyl bromide, were increased exponentially by the addition of MClO4 (M = Li and Na) and M(ClO4)2 (M = Mg and Ba); the extent of the cation effects increased as Na+ < Li+ < Mg2+ ≈ Ba2+, which was attributed to the “chemical” interaction between the metal ions and the leaving-group anions in the “aqueous” solution modified by the mixed-organic solvents and concentrated salts. Based on the Raman spectra, we discuss the distortion of the bulk water structure and the alteration of properties of water into those of a “non-aqueous” solvent with the addition of the organic solvents and concentrated salts (LiClO4 and Et4NBr) as well as with increasing temperature. However, the addition of non-metallic salts, i.e., Et4NX (X− = ClO4−, Cl−, Br−, and tosylate), caused decreases in the rates substantially, regardless of the leaving group (Cl or Br): the deceleration effects increasing as ClO4− < Br− < Cl− < TsO−. The deceleration in the solvolysis rates with Et4NX and R4NBr (R = Pr and n-Bu) should be caused by mainly the further decrease in water activity of the solvents. In addition, we would like to report solvolyses accompanied by “ion exchange” reactions for the typical SN2 substrates, hexyl chloride, bromide, and tosylate, in the sulfolane–H2O solvent.

Evidence for Different Types of Water Participation in the Solvolysis of 1-Adamantyl, tert-Butyl, and Methyl Chlorides from Density Functional Theory Computations

[structure: see text] The activation energy in the gas phase (deltaE(double dagger)) and the free energy of activation (deltaG(double dagger)) in water solution for the hydrolysis of the monohydrates of methyl chloride (MeCl), tert-butyl chloride (t-BuCl), and 1-adamantyl chloride (AdCl) have been computed with the B3LYP/631-G(d) method and the polarizable continuum (PCM) solvation model. There is a fair agreement between the deltaG(double dagger) values computed by us and the experimental data. The mechanistic implications of our computations are in severe contradiction with conventional representations. Thus, the computed nucleophilic solvent assistance (NSA) for the backside attack of a water molecule in the hydrolysis of MeCl is slightly lower than the corresponding NSA for t-BuCl. Hence, the hydrolysis of both MeCl and t-BuCl takes place mainly according to the classical S(N)2 mechanism. The most relevant difference is that deltaG(double dagger) for the frontside attack of water to t-BuCl is disfavored only by ca. 2 kcal/mol with regard to the backside attack but by ca. 23 kcal/mol in the case of MeCl. The higher solvolysis rate in water of t-BuCl in relation to AdCl is not due to steric factors affecting the specific solvation of the corresponding transition states, but to differential bulk solvent effects, which are accounted for by the PCM model.

Solvent-Equilibrated Ion Pairs from Carbene Fragmentation Reactions

[R(+) OC Cl(-)] ion pairs were generated in methanol/dichloroethane solutions, with R(+) as the 1-bicyclo[2.2.2]octyl, 1-adamantyl, or 3-homoadamantyl cation. Ion pairs were produced either by the direct fragmentation of alkoxychlorocarbenes (ROCCl), with R = 1-bicyclo[2.2.2]octyl, 1-adamantyl, or 3-homoadamantyl, or by the ring expansion-fragmentation of R'CH(2)OCCl, with R' = 1-norbornyl, 3-noradamantyl, or 1-adamantyl. Correlations of the [ROMe]/[RCl] product ratios as a function of the mole fraction of MeOH in dichloroethane showed that the homoadamantyl chloride ion pairs, produced by either the direct or ring expansion-fragmentations, were identical, solvent- and anion-equilibrated, and precursor independent. Laser flash photolysis experiments gave 20-30 ps as the time required for solvent equilibration and precursor independence. Methanol/chloride selectivities of the (less-stable) 1-adamantyl chloride and 1-bicyclo[2.2.2]octyl chloride ion pairs were not independent of their ROCCl or R'CH(2)OCCl precursors. Computational studies provided transition states for the fragmentations and for the structures of the ion pairs.

Kinetic solvent isotope effects and correlations of rates of solvolyses for α-methylthio and other substituted acetyl chloridesElectronic supplementary information (ESI) available: Tables S1–S3. See http://www.rsc.org/suppdata/p2/b2/b202664n/

Kinetic data for solvolyses of α-methylthioacetyl chloride, phenylthioacetyl chloride and thiophene-2-acetyl chloride in at least 33 aqueous solvent systems including 2,2,2-trifluoroethanol–ethanol solvent were determined at 10 °C by a conductimetric method, and their rates of solvolyses were correlated using Grunwald–Winstein type equations with the ionizing power parameter (YCl: based on the solvolyses of 1-adamantyl chloride) and the nucleophilicity parameter (NT). Kinetic solvent isotope effects (KSIEs) in water and methanol were investigated for the above compounds and in methanol also for phenyl, diphenyl, and trimethylacetyl and isobutyryl chlorides. The results show similar absolute rate constants, similar large amounts of nucleophilic solvent assistance, but different KSIE values (explained by general base catalysis).

Is the tert-butyl chloride solvolysis the most misunderstood reaction in organic chemistry? Evidence against nucleophilic solvent participation in the tert-butyl chloride transition state and for increased hydrogen bond donation to the 1-adamantyl chloride solvolysis transition state.

Despite theoretical calculations to the contrary, it has been argued that the 1-adamantyl cation is more stable than the tert-butyl cation in media of high dielectric constant. This argument has been utilized to suggest that the higher rate of solvolysis of tert-butyl chloride in aqueous ethanol is evidence for nucleophilic solvent participation in this classic reaction. Further, in "more highly ionizing" solvents, the rate of 1-adamantyl chloride is nearly the same as that of tert-butyl chloride, which is interpreted as a manifestation of the relative stabilities of the cations. However, the evidence cited does not explain the increased sensitivity of the rate of solvolysis of 1-adamantyl chloride over tert-butyl chloride to solvents which are better able to donate hydrogen bonds. The hypothesis developed here is that 1-adamantyl chloride solvolysis is assisted by hydrogen bond donation departing chloride ion to a greater extent than that of tert-butyl chloride solvolysis, most likely due to lessened steric interactions in a developing pyramidal cation. This hypothesis is supported by multiparameter solvent effect factor analyses utilizing the KOMPH2 equation which, in addition, quantifies the important role of ground-state destabilization due to strong solvent-solvent interactions. An important result from the good correlation of free energies of transfer of the tert-butyl chloride solvolysis transition state is that there is no change in mechanism, and, in particular, no nucleophilic participation even in non-hydroxylic basic solvents. The equation is also applied to the case of dimethylsulfonium ion solvolyses where the tert-butyl salt reacts substantially faster than the 1-adamantyl salt in ethanol and the gas phase. The decreased rate of the former in hydrogen bond donating solvents relative to the gas phase is as yet unclear. Solvent N values that were generated to characterize solvent nucleophilicity are shown not to be correlated by measures of solvent basicity but rather by the negative of measures of solvent hydrogen bond donor ability.

Concentrated salt effects on solvolysis rates in 1,4-dioxane–H2O mixed solvent and the expansion of the use of the Hammett equation for salt effects

In the mixed solvent system 50 vol% 1,4-dioxane and H2O, the concentrated salt effects of alkali metal (M+) and alkaline earth metal (M2+) perchlorates on the solvolysis rates of aliphatic halides (RX) and related compounds were investigated. The “pseudo” first-order reaction rates (k/s−1) of typical SN1 substrates, 1-adamantyl chloride and bromide and tert-butyl chloride, increased exponentially with increasing concentration of metal salt. The effects of M2+ on the reaction rates were larger than those of M+: Na+, Li+ < Ba2+ < Mg2+. A non-metallic salt, Et4NBr, at concentrations of ≥1.0 mol dm−3 caused the log k value to decrease, although the log k was slightly increased by lower concentrations of the salt (<1.0 mol dm−3). Raman spectra of D2O containing high concentrations of Et4NBr suggested a complete distortion of the solvent structure. The increase in log k values in the presence of metal ions was explained by direct “chemical” interaction between halide ions and metal ions with the concentrated salts in the modified media: X−⋯M+ or X−⋯M2+. The solvolysis rates of typical SN2 substrates, ethyl bromide and methyl tosylate, were much decreased by the addition of concentrated LiClO4. The log k values of borderline SN1–SN2 reacting substrates, isopropyl bromide and benzyl halides, remained almost constant, however, more positive slopes in log k in the presence of LiClO4 were caused by the introduction of methyl substituents on benzyl halides; negative slopes were observed upon the introduction of strong electron-withdrawing substituents, such as NO2 and CN. We observed a correlation (of two different slopes) between the σ+ values in the Hammett equation and the Δlog k for substituted benzyl halides upon the addition of 1.0 mol dm−3 LiClO4, as well as between the log (kx/kH) values themselves. We propose here an expansion of the use of the Hammett equation for the concentrated salt effect.

The Standard Enthalpy of Formation of the 1-Adamantyl Cation in the Gas Phase. An Experimental and ab Initio Re-assessment

The standard molar enthalpy of formation of gaseous 1-adamantyl chloride (1Cl,g) was determined experimentally by means of thermochemical techniques. Ab initio quantum-chemical calculations at the G2(MP2) level were performed on adamantyl cation (1+) and on 1Cl. Combination of these data with other experimental and computational results for adamantane (1H), isobutane (2H), tert-butyl cation (2+), and tert-butyl chloride (2Cl) provided purely experimental and purely computational, independent values for the standard enthalpy and Gibbs energy changes for reactions 1 and 2: where X = Cl. This information was used to determine a value of 162.0 ± 2.0 kcal mol-1 for the standard molar enthalpy of formation of gaseous 1+, ΔfH°m(1+,g).

Concentrated Salt Effects on the Solvolysis Reaction Rates in Methanol–Water Solution

Abstract The solvolysis rates of aliphatic halides and related compounds (RX) were determined in an 80 vol% MeOH–20 vol% H2O solvent in the presence of very highly concentrated salts (0.25—5.0 mol dm−3) at 25—75 °C. For typical SN1 substrates, such as 1-adamantyl bromide and t-butyl chloride, the pseudo-first-order reaction rates (k/s−1) increased exponentially with increasing concentration of LiClO4, NaClO4, Mg(ClO4)2, and Ba(ClO4)2. The cation effects increased as Na+ &amp;lt; Li+ &amp;lt; Ba2+ ≤ Mg2+. A nonmetallic salt, Et4NBr, caused the k/s−1 value for 1-adamantly bromide to be slightly increased at lower concentrations ( &amp;lt; 1.0 mol dm−3), but to be greatly decreased at higher salt concentrations ( ≥ 2.0 mol dm−3). The large positive effects of metal perchlorates were explained by a change in the solvent structure and the formation of “stable” carbocations through a “chemical” interaction between X− (Cl−, Br−, or I−) and M+ (Li+, Na+) or M2+ (Mg2+, Ba2+) in the “modified” solvent. On the other hand, for SN1–SN2 intermediates, the solvolysis reaction rates were decreased by a decrease in the activity of the solvent containing a large amount of salts. The apparent rate constant (“k/s−1”) for isopropyl bromide at 75 °C remained an almost constant value in the presence of 0—5.0 mol dm−3 LiClO4. The rate constant for ethyl bromide was decreased substantially by the addition of the alkali metal and alkaline-earth metal perchlorates. A good linearity was observed between log (k1/k0) and the m values for RX by Grunwald and Winstein, where k1 and k0 are the solvolysis rates in the presence of 1.0 mol dm−3 LiClO4 and in the absence of the salt, respectively. Upon the solvolysis of neophyl chloride (1-chloro-2-methyl-2-phenylpropane), the change in the reaction scheme (e.g., methyl shift) was suspected during the increase in the LiClO4 or Ba(ClO4)2 concentration.

Extremely Large Acceleration of the Solvolysis of 1-Adamantyl Chloride upon Incorporation of a Spiro Adamantane Substituent: Solvolysis of 1-Chlorospiro[adamantane-2,2'-adamantane

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExtremely Large Acceleration of the Solvolysis of 1-Adamantyl Chloride upon Incorporation of a Spiro Adamantane Substituent: Solvolysis of 1-Chlorospiro[adamantane-2,2'-adamantane]John S. Lomas, Malcolm J. D'Souza, and Dennis N. KevillCite this: J. Am. Chem. Soc. 1995, 117, 21, 5891–5892Publication Date (Print):May 1, 1995Publication History Published online1 May 2002Published inissue 1 May 1995https://doi.org/10.1021/ja00126a045RIGHTS & PERMISSIONSArticle Views87Altmetric-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 InReddit PDF (285 KB) Get e-Alerts Get e-Alerts

Limitations of the transition state variation model. Part 2. Dual reaction channels for solvolyses of 2,4,6-trimethylbenzenesulphonyl chloride

Rate constants for solvolyses of 2,4,6-trimethylbenzenesulphonyl chloride (1) are reported for aqueous binary mixtures with acetone, acetonitrile, dioxane, ethanol and methanol. Kinetic solvent isotope effects in water and in methanol and product selectivities in alcohol–water mixtures are also reported. Additional YCl values have been determined for aqueous acetonitrile and dioxane from rate constants for solvolyses of 1-adamantyl chloride. Contrary to earlier reports, correlations between logarithms of rate constants for solvolyses of 1vs. Y or YCl are approximately bilinear. From these plots the rate data are dissected into contributions from two competing reaction channels, and this interpretation is supported for alcohol–water mixtures by the trends of product selectivities, which show maxima close to the solvent compositions where there are breaks in the rate–rate profiles. Greater rate constants for 40% v/v ethanol–water than for 97% w/w trifluoroethanol–water (solvents of approximately equal ionizing power) show the importance of nucleophilic solvent assistance (SN2 character) even for the reaction channel favoured in more polar media. Hence, in agreement with an earlier consensus, neither of the reaction channels corresponds to an SN1 mechanism. From the kinetic solvent isotope effect of 1.68 in methanol, it is proposed that the reaction channel favoured in less polar media is general-base catalysed and/or is possibly an addition–elimination pathway.

Trends in selectivity. Evidence from rates and products for simultaneous reaction channels in solvolyses of benzoyl chloride and substituted derivatives

Rates of solvolyses of para-Z-substituted benzoyl chlorides (Z = OMe, Me, or Cl) are reported for highly aqueous binary mixtures (with acetone, ethanol, and methanol cosolvents). Product data (ester and acid) are reported for a wide range of compositions of the aqueous binary alcohol mixtures (for Z = Me, H, or Cl). As water is added to alcohol, the selectivity S([ester][water]/[acid][alcohol] initially increases but then reaches a plateau and/or decreases. This reversal of the trend in S occurs at different solvent compositions for each substrate (Z = Me, H, or Cl) and is very close to the region of mechanistic change predicted previously from rate–rate profiles; these predictions have now been refined by replacing solvolyses of 1-adamantyl chloride by p-methoxybenzoyl chloride as the model SN1 process. The results provide new and sharply defined evidence for mechanistic change in nucleophilic substitutions at acyl carbon, supporting the co-existence of two different mechanisms or reaction channels, each of which could show variable structures of transition states. A quantitative dissection of observed rates into contributions from two reaction channels is described, and an attempt is made—with partial success—to calculate variations in S values occurring as the mechanism changes. Trends in S values are calculated successfully.

Weakly nucleophilic leaving groups. Solvolyses of 1-adamantyl and t-butyl heptafluorobutyrates and trifluoroacetates

Kinetic data are reported for solvolyses of 1-adamantyl and t-butyl heptafluorobutyrates and trifluoroacetates in binary aqueous mixtures with acetone, ethanol, and methanol and in 97% trifluoroethanol–water and hexafluoropropan-2–ol-water. Logarithms of solvolysis rates for t-butyl heptafluorobutyrate compared with t-butyl chloride (Figure 3) and with 1-adamantyl heptafluorobutyrate (Figure 4) show the relatively low reactivity of solvolyses of t-butyl heptafluorobutyrate in fluorinated alcohols, consistent with nucleophilic solvent assistance for solvolyses of t-butyl heptafluorobutyrate in the more nucleophilic solvents (e.g. aqueous methanol). In 97% hexafluoropropan-2-ol–water, 1-adamantyl heptafluorobutyrate solvolyses faster than t-butyl heptafluorobutyrate, supporting a recent prediction. Comparisons of relative rates of solvolyses of 1-adamantyl trifluoroacetate with those of 1-adamantyl chloride (Figure 2) and with YOTs(Figure 5) show the absence of substantial effects on relative rates due to electrophilic solvent assistance by fluorinated alcohols, other than those already included in the Y values. Solvolyses of triflates are anomalous in comparison with solvolyses involving other weakly nucleophilic leaving groups (perchlorate, trifluoroacetate, and heptafluorobutyrate).

Effect of solvent on the reactions of coordination complexes. Part 2.—Kinetics of solvolysis of cis-(chloro)(imidazole)bis(ethylenediamine)-cobalt(III) and cis-(chloro)(benzimidazole)bis(ethylenediamine)cobalt(III) in methanol–water and ethylene glycol–water media

The kinetics of solvolysis of cis-(chloro)(imidazole)bis(ethylenediamine)-cobalt(III) and cis-(chloro)(benzimidazole)bis(ethylenediamine)cobalt(III) have been investigated in aqueous methanol (MeOH) and aqueous ethylene glycol (EG) media (0–80% by weight of MeOH or EG) at 45–64.7 °C. The logarithm of the pseudo-first-order rate constants for MeOH–water media exhibits linear dependence with the reciprocal of the bulk dielectric constant (D–1s), the mole fraction of MeOH (XMeOH) and the solvent ionizing power Y(Y1-AdCl) as determined by the solvolysis rates of 1-adamantyl chloride. Similar plots (log ksobsvs.xEG or D–1s) for EG–water media are non-linear. It is evident that the solvation phenomenon plays dominant role and the rate of solvolysis is mediated by the dual solvent vectors, the overall acidity and basicity of the solvent mixtures. The relative transfer free-energy calculations indicate that the mixed solvent media exert more destabilizing effect on the transition state as compared to the initial state. The activation enthalpy and entropy vs.Xorg(where Xorg is the mole fraction of the organic solvent component) plots display maxima and minima indicating that the solvent structural changes play significant role in the activation process. The activation free energy at a given temperature, however, increases only marginally and linearly with increasing Xorg. The mutual compensatory effect of activation enthalpy and entropy on the activation free energy is in keeping with the fact that the perturbations of the reaction zone and the solvent network remain approximately proportional to each other with increasing Xorg so that the isodelphic and the lyodelphic components of ΔH± and ΔS± correlate well with each other.

Effect of solvent on the reactions of coordination complexes. Part 1.—Kinetics of solvolysis of cis-(bromo)(benzimidazole)bis(ethylenediamine)cobalt(III) in methanol–water media

The kinetics of the solvolytic aquation of cis-(bromo)(benzimidazole)bis(ethylenediamine)cobalt(III) have been investigated at 35, 40, 45, 50.2 and 54.8 °C in aqueous methanol media of methanol content 0–80 wt %. The pseudo-first-order rate constant decreases with increasing methanol content. Plots of log ksaqvs. D–1s(where Ds is the dielectric constant of the solvent mixture) and log ksaqvs. the Grunwald–Winstein Y parameter or revised YCl(1-adamantyl Chloride) parameter are non-linear. The plot of log ksaqvs. the molefraction of methanol (XMeOH), which deviates from linearity at 35, 40 and 45 °C, is an excellent straight line (r= 0.998) at 50 and 54.8 °C over the entire composition range studied. It is evident that the solvation phenomenon plays dominant role and that the rate of aquation is mediated by the dual solvent vectors, the overall basicity and acidity of the solvent mixtures. At 25 °C the calculated values of the transfer free energy of the dissociative transition state, cis-{[Co(en)2(bzmH)]3+}*, relative to that of the initial state, cis-[Co(en)2(bzmH)Br]2+, for the transfer of the ions from water to the mixed solvent were positive at all solvent compositions (except 80 % MeOH), exhibiting a maximum at XMeOH= 0.46. This reflects the propensity of the said tripositive transition state and the dipositive initial state towards solvation interaction with the medium. In contrast to the activation free energy, which varies linearly with XMeOH, the plots of activation enthalpy and entropy against XMeOH exhibit maxima at XMeOH= 0.12 and 0.46 and minima at XMeOH= 0.02 and 0.25; thereafter both ΔH‡ and ΔS‡ decrease steeply to significantly low values at XMeOH= 0.69 (ΔH‡= 80.1 ± 4.3 kJ mol–1 and ΔS‡=–91 ± 13 J K–1 mol–1), manifesting the effect of solvent-shell reorganisation around the complex ion both in the initial state and in the transition state as the composition is varied.

Linear solvation energy relationships. Part 37. An analysis of contributions of dipolarity–polarisability, nucleophilic assistance, electrophilic assistance, and cavity terms to solvent effects on t-butyl halide solvolysis rates

Solvolysis/dehydrohalogenation rates of t-butyl chloride in 21 hydrogen bond donor (HBD) and non-HBD solvents are well correlated (r= 0.9973, s.d. = 0.24) by the equation: log k=–14.60 + 0.48λH2/100 + 5.10π*+ 4.17α+ 0.73β where δH2 is the solvent cohesive energy density, and π*, α, and β are the solvatochromic parameters that scale solvent diplority–polarizability, HBD acidity (electrophilicity), and hydrogen-bond acceptor basicity (nucleophilicity). In the corresponding equation over the same solvent set for t-butyl bromide, the terms in δH2 and α are smaller still, and the terms in δH2 and β are not statistically significant. It is shown that a trifluoroethanol (TFE)–ethanol plot, wherein ButCl and 1-adamantyl chloride (1-AdCl) solvolysis rates are compared, can be interpreted as evidence for electrophilic assistance of 1-AdCl in TFE rather than the more usual interpretation of nucleophilic assistance to ButCl in EtOH–H2O.

The SN2-SN1 spectrum. 4. The SN2 (intermediate) mechanism for solvolyses of tert-butyl chloride: a revised Y scale of solvent ionizing power based on solvolyses of 1-adamantyl chloride

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe SN2-SN1 spectrum. 4. The SN2 (intermediate) mechanism for solvolyses of tert-butyl chloride: a revised Y scale of solvent ionizing power based on solvolyses of 1-adamantyl chlorideT. William Bentley and Gillian E. CarterCite this: J. Am. Chem. Soc. 1982, 104, 21, 5741–5747Publication Date (Print):October 1, 1982Publication History Published online1 May 2002Published inissue 1 October 1982https://doi.org/10.1021/ja00385a031RIGHTS & PERMISSIONSArticle Views1597Altmetric-Citations204LEARN 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 (887 KB) Get e-Alerts Get e-Alerts