Solvent-assisted alcohol-isocyanate kinetics

Draye, Anne-Cécile; Tarasov, D. N.; Tondeur, J. J.

doi:10.1007/bf02475790

Cited by 19 publications

(14 citation statements)

References 6 publications

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“…They depend on the polarity and Η-bonding properties of the solvent, which bring about changes in the rate equation and so modify the observed reaction order in a way logically similar to that reported about the uncatalyzed mechanism [5,11]. The existence of a Ν ->Sn complex would prevent Hbonding from alcoholic OH groups to the Ν atom ofNCO so that only interactions between Ο atoms of ROH and C of isocyanate would remain possible, as far as the Ο atom of isocyanate is not involved [12],…”

Section: (Roh)" + =Sn(oocr'); = =Sn(or)(oocr') + R'cooh + (Roh)« Kmentioning

confidence: 63%

“…The chemicals, their purification [10] and the spectrophotometric UV (283 nm, in DBE and 282 nm, in ACN) and FTIR (2261 cm' 1 in Tol) procedures were described in previous papers [1][2][3] as well as the effect of temperature on UV extinction coefficients [5], As formerly [2,3], the kinetic runs were performed in the presence of a stoichiometric excess of cyclopentanol able to generate a pseudo-first order rate constant k, gathering the added contributions of the catalyzed (k c ) and of the uncatalyzed (k" c ) reactions [5,11].…”

Section: Methodsmentioning

confidence: 99%

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Solvent Effects on an Organotin-Catalyzed Alcohol-Isocyanate Reaction

Draye¹,

Tondeur²,

Тигер³

1999

Main Group Metal Chemistry

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The pseudo-first order kinetics of the reaction of cyclopentanol with phenylisocyanate, catalyzed by dibutyltin di(2-ethylhexanoate) (DBTDEH), was studied by means of UV and IR spectrophotometry. Reaction orders with respect to catalyst and to monomeric alcohol [1] were considered in toluene (Tol), di(nbutyl)ether (DBE) and acetonitrile (ACN). The results, which were interpreted with the aid of rate equations previously derived [2-4] on the basis of a reaction scheme involving an alkoxytin(IV) intermediate, indicate that pre-reaction complexes of solvent-dependent composition are formed in the rate determining step of both catalyzed and uncatalyzed mechanisms [5], INTRODUCTIONPrior studies related to the organotin-catalyzed nucleophilic addition of alcohol in excess to isocyanate have shown that this reaction is first order in isocyanate. The so obtained pseudo-first order rate constants do not vary linearly with the concentration of alcohol or of catalyst. Various kinetic behaviours were reported. For Borkent [6] the order is close to 0.5 in catalyst and results from the presence of a cationic active intermediate R 3 Sn + while for Van der Weij [7] the value 0.5 found with respect to both catalyst and alcohol reflects the formation of an ionizable alcohol-catalyst complex. Such interpretations are questionable since these reactions are also easy in apolar solvents. For Entelis et al.[8] a ceiling of the rate, observed at high alcohol and catalyst concentrations, should be due to a partial blocking of reacting species by nonproductive reactant(s)-catalyst homo-and/or heteroassociates. Bloodworth and Davies [9], considering the high reactivity of tin alkoxides towards isocyanate, suggested the tin carboxylate to be partly alcoholyzed to an active alkoxytin catalyst (scheme 1). This type of reaction scheme is also supported by some of our experiments dealing with the decelerating effect exerted by carboxylic acids or thiols [2,3], However, in the former works, the order was generally determined with respect to the overall alcohol content. The molecular meaning of the found values is questionable since associated OH groups exhibit a much smaller reactivity than free ones, so that any interpretation of the kinetic influence of alcohol must logically take into account its solvent-dependent sharing among free and associated forms [1],

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Section: (Roh)" + =Sn(oocr'); = =Sn(or)(oocr') + R'cooh + (Roh)« Kmentioning

confidence: 63%

Section: Methodsmentioning

confidence: 99%

Solvent Effects on an Organotin-Catalyzed Alcohol-Isocyanate Reaction

Draye¹,

Tondeur²,

Тигер³

1999

Main Group Metal Chemistry

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“…For this latter, four molecules are believed to associate with the isocyanate in the reactive complex [4], what is likely a structure making factor able to induce an entropy loss, while the energy consumption for breaking already present Η-bonds would be more or less compensated by the energy evolved by the complexation. For the catalyzed reaction the number of molecules entering the reactive 500 Brought to you by | Purdue University Libraries Authenticated Download Date | 6/14/15 1:24 PM complex is assumed to be smaller, which means that the structure-making effect likely decreases and that consequently the activation entropy reaches less negative values.…”

Section: Discussionmentioning

confidence: 98%

“…Variable fractional orders were found with respect to catalyst and to alcohol and were interpreted with the help (a) of data related to the ratio of monomeric alcohol in the used solvents [3], which is considered as the most reactive alcohol species towards isocyanate [4], (b) of rate laws derived from a reaction scheme (scheme l) [5][6][7][8] in which the catalysis would mainly proceed through a scarcely active monoalkoxytin(IV) able to form with isocyanate and alcohol and/or solvent molecule(s) a pre-reaction complex. This latter would, in the rate determining step, turn into a N-stannylcarbamate easily alcoholysed to yield urethane and restore the catalytic active species.…”

Section: Introductionmentioning

confidence: 99%

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Activation Parameters of an Organotin Catalyzed Alcohol-Isocyanate Reaction

Draye¹,

Tondeur²

1999

Main Group Metal Chemistry

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In this paper, the kinetics of the reaction of phenylisocyanate with cyclopentanol, catalyzed by di(n-butyl)tin di-(2-ethylhexanoate) (DBTDEH), was studied at different temperatures in the same solvents as previously [1], i.e in acetonitrile (ACN), di-(n-butyl)ether (DBE) and toluene (Tol), in order to determine the Arrhenius energy, which is shown to be larger in the presence of the tin(IV) catalyst than in its absence [2], and the apparent activation entropy, which was derived from the values of the extrapolated intercepts of the In k-//7"graphs. The results demonstrate that entropic configurational effects are the prevailing cause of the accelerating effect of the tin(IV) catalyst on this reaction.

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Effects of solvent polarity on the reaction of phenol with tolylene‐2,4‐diisocyanate

Yang¹,

Han²,

Li³

et al. 2011

J of Applied Polymer Sci

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Using tolylene-2,4-diisocyanate as standard compound, the relationship between ANCO absorbance and concentration was studied with in situ FTIR. The linear relationship appeared correct only for concentrations lower than 0.4 mol L À1 . Then, the urethane reaction kinetics of phenol with tolylene-2,4-diisocyanate were investigated in different solvents, such as dimethyl sulfoxide, cyclohexanone, n-butyl acetate, 1,4-dioxane, and xylene. It showed that solvents largely affected reaction rates. The reaction was largely accelerated in polar solvents, following the order of dimethyl sulfoxide > cyclohexanone > n-butyl acetate > 1,4-dioxane > xylene. It was in contrast to the alcohol-diisocyanate reaction. Finally, an appropriate reaction mechanism was proposed. The HAO bond in phenol was polarized under the influence of solvents, which made the combination of hydrogen to nitrogen and alkoxyl group to carbenium easier. After that the solvent was dissociated and the carbamate generated. The kinetic equation could be derived as

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Solvent-assisted alcohol-isocyanate kinetics

Abstract: The dependence of the reaction rate of cyclopentanol with phenyl isocyanate on the concentration of monomeric alcohol [1] in toluene, di-n-butyl ether and acetonitrile suggests a reaction scheme involving various complexes.

Cited by 19 publications

References 6 publications

Solvent Effects on an Organotin-Catalyzed Alcohol-Isocyanate Reaction

Solvent Effects on an Organotin-Catalyzed Alcohol-Isocyanate Reaction

Activation Parameters of an Organotin Catalyzed Alcohol-Isocyanate Reaction

Effects of solvent polarity on the reaction of phenol with tolylene‐2,4‐diisocyanate

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