Kinetics of the Alcoholysis of Acetyl Chloride in Ethanol.

Euranto, Erkki K.; Leimu, R.; Rymo, Lars; Bowie, John H.; Williams, D. H.; Bunnenberg, E.; Djerassi, Carl; Records, Ruth

doi:10.3891/acta.chem.scand.20-2028

Cited by 8 publications

(5 citation statements)

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“… a Calculated from the molar ratios of solvents given in Table of ref , and from the ester/acid molar ratios determined by HPLC analyses of 10 -2 M solutions; measurements were made by duplicate analyses of at least two independent solutions and errors shown are average deviations. b A value of S = 0.98 can be calculated from the fraction of ester (0.233) obtained from the difference between titrations for acid and for chloride ion (ref ). …”

Section: Resultsmentioning

confidence: 99%

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S_N2 Mechanism for Alcoholysis, Aminolysis, and Hydrolysis of Acetyl Chloride

1996

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First-order solvolysis rate constants are reported for solvolyses of acetyl chloride in methanol and MeOD, and in binary aqueous mixtures with acetone, acetonitrile, ethanol, methanol, and trifluoroethanol at 0 degrees C. Product selectivities (S = [MeCOOR]/[MeCOOH] x [water]/[alcohol]) are reported for solvolyses in ethanol/ and methanol/water at 0 degrees C. Solvolyses of acetyl chloride show a high sensitivity to changes in solvent ionizing power, consistent with C-Cl bond cleavage. As the solvent is varied from pure ethanol (or methanol) to water, S values and rate-rate profiles show no evidence for the change in reaction channel observed for solvolyses of benzoyl and trimethylacetyl chlorides. However, using rate ratios in 40% ethanol/water and 97% trifluoroethanol/water (solvents of similar ionizing power but different nucleophilicities) to compare sensitivities to nucleophilic attack, solvolyses of acetyl chloride are over 20-fold more sensitive to nucleophilic attack than benzoyl chloride. The solvent isotope effect of 1.29 (MeOH/MeOD) for acetyl chloride is similar to that for p-methoxybenzoyl chloride (1.22) and is lower than for benzoyl chloride (1.55). Second-order rate constants for aminolyses of acetyl chloride with m-nitroaniline in methanol at 0 degrees C show that acetyl chloride behaves similarly to p-methoxybenzoyl chloride, whereas benzoyl chloride is 40-fold more sensitive to the added amine. The results indicate mechanistic differences between solvolyses of acetyl and benzoyl chlorides, and an S(N)2 mechanism is proposed for solvolyses and aminolyses by m-nitroaniline of acetyl chloride (i.e. these reactions are probably not carbonyl additions, but a strong sensitivity to nucleophilic attack accounts for their high rates).

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Section: Resultsmentioning

confidence: 99%

“…Acetyl chloride was distilled before use, but NMR showed about 0.5% of acid impurity (by comparison of the signal for MeCOOH with the 13 C satellite of MeCOCl). It was found previously that freshly-distilled acetyl chloride is partially hydrolyzed (up to 4%) during manipulations …”

Section: Methodsmentioning

confidence: 99%

S_N2 Mechanism for Alcoholysis, Aminolysis, and Hydrolysis of Acetyl Chloride

1996

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“…The mixed carboxylic–sulfonic anhydrides react faster than either the carboxylic or sulfonic anhydrides due to the combination in the substrate of a good leaving group with an acyl carbon which is favorable to either nucleophilic attack or to ionization to a resonance‐stabilized acylium ion. The ethanolyses, for example, are considerably faster for acetyl p ‐toluenesulfonate ( 1 ) than for acetyl chloride and, at 0 °C, a specific rate of 1.83 × 10 −2 s −1 for acetyl chloride can be compared to an extrapolated value, using the data of Table , of 13.4 s −1 for 1 , leading to a k OTs / k Cl ratio of 7.3 x 10 2 .…”

Section: Discussionmentioning

confidence: 99%

Correlation of the rates of solvolysis of acetic p‐toluenesulfonic anhydride (acetyl p‐toluenesulfonate) and a comparison with acetyl halides

Kevill

Ryu

2013

J of Physical Organic Chem

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The specific rates of solvolysis of acetyl p-toluenesulfonate have been measured by a rapid-response conductivity technique at temperatures in the temperature range of À10 to À55 C. For 13 solvents at À39.6 C, an extended Grunwald-Winstein equation correlation led to sensitivities to changes in solvent nucleophilicity of 0.56 and to changes in solvent ionizing power of 0.61. In 89.1% acetone at À20 C, the comparison with acetyl bromide solvolysis led to a k OTs / k Br ratio of 1.4. In methanol and methanol-d at À39.6 C, the solvent deuterium isotope effect k MeOH /k MeOD is 0.99. These results are consistent with an S N l reaction with appreciable nucleophilic solvation or an S N 2 reaction with a loose transition state. These two approaches lead to similar structures for the transition state. A solution of the acetyl p-toluenesulfonate was conveniently prepared by the rapid reaction of acetyl chloride with silver p-toluenesulfonate in acetonitrile.

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“…The activation energy of this reaction is approximately 13 kcal mol À1 . [19][20][21] To detect the aforementioned reaction intermediate, a fast reagent-mixing setup was designed based on two separate syringes, each delivering approximately 3 mL of acetyl chloride or ethanol into separate stainless-steel tubes. As the tubes are brought together, the droplets touch for approximately 100 ms.…”

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confidence: 99%