Rates of Solvolysis of Some Alkyl Fluorides and Chlorides<sup>1</sup>

Swain, C. Gardner; Scott, C. B.

doi:10.1021/ja01097a520

Cited by 197 publications

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“…The consideration of fluoride/chloride ratios (k F /k Cl ) in nucleophilic substitution reactions has long been recognized as a useful tool in studying the reaction mechanism [17]. This is especially so when the attack is at an acyl carbon.…”

Section: Discussionmentioning

confidence: 99%

“…This is especially so when the attack is at an acyl carbon. For S N 1 reaction, a value as low as 10 -7 was observed in 4-(N,Ndimethylamino)benzoyl halide solvolyses [18] and a low value of 1.3·10 -4 was also observed for acetyl halide solvolyses in 75% acetone [17]. These values reflect an appreciable ground-state stabilization for the fluoride [19] and the need to break a strong carbon-fluorine bond in the rate determining step.…”

Section: Discussionmentioning

confidence: 99%

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Rate and Product Studies of Solvolyses of Benzyl Fluoroformate

Kyong

Ryu

Kevill

2006

IJMS

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Abstract:The specific rates of solvolysis of benzyl fluoroformate have been measured in several hydroxylic solvents at 25.0 °C. For methanolysis, the solvent deuterium isotope effect and activation parameters were determined and activation parameters were also determined for solvolyses in ethanol and 80% ethanol. For several of the binary hydroxylic solvents, measurement of product ratios allowed selectivity values to be determined. An extended Grunwald-Winstein treatment of the data led to sensitivities to changes in solvent nucleophilicity and ionizing power. Comparison with previously determined specific rates for solvolysis of the chloroformate gave fluorine/chlorine rate ratios greater than unity. All of the determinations made were consistent with an addition-elimination (associationdissociation) mechanism, with addition rate-determining.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Rate and Product Studies of Solvolyses of Benzyl Fluoroformate

Kyong

Ryu

Kevill

2006

IJMS

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“…5, Nuc = SCN -) is an encounter-controlled process. The reactivity of this carbocation should be similar to that of the p-methoxybenzyl cation, whose capture by azide ion is encounter-controlled [7], and since thiocyanate ion is a better nucleophile than azide ion [8], the reactions of thiocyanate with these carbocations should be encounter-controlled as well. Use of the encounter-controlled rate constant k N = 5 × 10 9 M -1 s -1 and the value of the observed rate constant for thiocyanate, k obs = (9.6 ± 0.8) × 10 M -2 s -1 , in the rate law for the process of eq.…”

Section: O-quinone Methidementioning

confidence: 99%

Reactive intermediates. Some chemistry of quinone methides

Chiang

Kresge

Zhu

2000

Pure and Applied Chemistry

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Quinone methides were produced in aqueous solution by photochemical dehydration of o-hydroxybenzyl alcohols (o-HOC 6 H 4 CHROH; R = H, C 6 H 5 , 4-CH 3 OC 6 H 4 ), and flash photolytic techniques were used to examine their rehydration back to starting substrate as well as their interaction with bromide and thiocyanate ions. These reactions are acid-catalyzed and show inverse isotope effects (k H+ /k D+ < 1), indicating that they occur through preequilibrium protonation of the quinone methide on its carbonyl carbon atom followed by rate-determining capture of the benzyl carbocations so formed by H 2 O, Br -, or SCN -. With some quinone methides (R = C 6 H 5 and 4-CH 3 OC 6 H 4 ) this acid catalysis could be saturated, and analysis of the data obtained in the region of saturation for the example with R = 4-CH 3 OC 6 H 4 produced both the equilibrium constant for the substrate protonation step and the rate constant for the rate-determining step. Energy relationships comparing the quinone methides with their benzyl alcohol precursors are derived.

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“…Removal of water was followed by examination of the 'Hmr spectrum (D20), which consisted of two prominent triplets at 3.13 and 3.93 pprn due to HOCH2CH2S03-, two very small triplets at 3.4 and 3.9 pprn due to 4a (-2%), but with no sign whatever of any signals ascribable to HOCH2CHDS03-. At this stage we set a chemically reasonable limit to the raiige of (k4/k3)C1 (and hence kLl/k3) values, and to this end make use of the Swain-Scott s parameter (19). Values of s ranging from 0.69 to 0.82 have been reported for reactions of sulfonic esters (37).…”

Section: Sodium 3-hydroxypropanesulfonate (6)mentioning

confidence: 99%

“…[A141 and [A16]. One of these procedures involved calculating values for the rate constant ratios by taking a value of (k4/k3)CI that would yield a Swain-Scott s parameter (19) is the observation that a significant rate reduction was seen when the reaction was carried out in the presence of either sodium p-toluenesulfonate or sodium p-sulfanilate; specifically, for 0.2M solutions (at pH 6.0 and 25.0°C) the rate constant with p-CH3C6H4sO3-Na+ was 8.56 X s-' and that with p-NH2C6H4S03-Na+, 5.72 X s-'. These values may be compared with kobs values (at pH 6.0) of 1.70 x lop2 s-' with 0.3 M NaC1, and 5.50 X lop2 s-' with 0.3 M NaC104.…”

mentioning

confidence: 99%

The mechanism of hydrolysis of 2-hydroxyethanesulfonyl chloride: the intermediacy of 1,2-oxathietane 2,2-dioxide (β-sultone)

King¹,

Khemani²

1989

Can. J. Chem.

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JAMES FREDERICK KING and KISHAN CHAND KHEMANI. Can. J. Chem. 67, 2162 (1989). The hydrolysis of 2-hydroxyethanesulfonyl chloride (1) has been investigated with the aid of kinetic and product analysis studies. .The results are quantitatively consistent with the mechanism of hydrolysis shown in Scheme 1, the chief features of which are (a) formation of p-sultone (2) and its rapid further reaction (the major pathway), together with (b) a minor direct hydrolysis route. The kinetics of both the p-sultone formation and the direct hydrolysis shows two terms, one first order in 1 alone, and the other first order in hydroxide as well; the rates of the first-and second-order reactions are lowered by added sodium chloride. It is suggested (a) that the unimolecular p-sultone formation involves 1 in a complex with water (as in 9) and that the water acts as a general base in the cyclization to 2, and (b) the hydroxide-promoted reaction proceeds by cyclization of the conjugate base of 1 (i.e., 10). The unimolecular direct hydrolysis is regarded as a conventional hydrolysis of a sulfonyl chloride with attack of the water with general base assistance from a second water molecule. The hydroxide-promoted direct reaction in D20 leads to no uptake of deuterium, showing that the reaction does not go by way of the sulfene, and a reaction by way of a six-membered cyclic transition state is tentatively proposed. Evidence is presented that the chloride ion rate suppression is not primarily due to reaction of p-sultone with C1-to give back 1; the possible origins of the effect are discussed.Key words: sulfonyl chlorides, 2-hydroxyethanesulfonyl chloride, p-sultone, kinetics of sulfonyl chloride hydrolysis, mechanisms of sulfonyl chloride hydrolysis. La cinCtique de la formation de la p-sultone ainsi que de I'hydrolyse directe prCsente A chaque fois deux termes : I'un du premier ordre uniquement en composC 1 et I'autre qui est en plus du premier ordre en ion hydroxyde; les vitesses des rkactions du premier et du deuxikme ordre sont abaissCes par l'addition de chlorure de sodium. On sugghe : (a) que la formation unimolCculaire de la p-sultone implique que le compost5 1 est complexC dans I'eau (comme dans 9) et que I'eau agit comme base gCntrale dans la cyclisation conduisant au compost 2 et (b) que la rCaction catalysCe par I'ion hydroxyde se produit par le biais d'une cyclisation de la base conjuguCe du composC 1 (soit 10). On considkre I'hydrolyse unimolCculaire directe comme une hydrolyse conventionnelle d'un chlorure de sulfonyle impliquant une attaque de I'eau avec l'assistance d'une seconde molCcule d'eau agissant comme base gCnCrale. L'hydrolyse directe, dans le D 2 0 et sous I'influence d'ions hydroxydes, ne provoque aucune incorporation de deuttrium; ce rCsultat dCmontre que la reaction ne se produit pas par le biais du sulfene et on propose provisoirement que la rCaction se produit via un Ctat de transition cyclique A six chalnons. On prksente des donntes dCmontrant que le ralentissement de la reaction sous I'iduence d'ions chloru...

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Rates of Solvolysis of Some Alkyl Fluorides and Chlorides¹

Cited by 197 publications

References 0 publications

Rate and Product Studies of Solvolyses of Benzyl Fluoroformate

Rate and Product Studies of Solvolyses of Benzyl Fluoroformate

Reactive intermediates. Some chemistry of quinone methides

The mechanism of hydrolysis of 2-hydroxyethanesulfonyl chloride: the intermediacy of 1,2-oxathietane 2,2-dioxide (β-sultone)

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Rates of Solvolysis of Some Alkyl Fluorides and Chlorides1

Cited by 197 publications

References 0 publications

Rate and Product Studies of Solvolyses of Benzyl Fluoroformate

Rate and Product Studies of Solvolyses of Benzyl Fluoroformate

Reactive intermediates. Some chemistry of quinone methides

The mechanism of hydrolysis of 2-hydroxyethanesulfonyl chloride: the intermediacy of 1,2-oxathietane 2,2-dioxide (β-sultone)

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Rates of Solvolysis of Some Alkyl Fluorides and Chlorides¹