Activation Parameters of an Organotin Catalyzed Alcohol-Isocyanate Reaction

Draye, Anne-Cécile; Tondeur, J. J.

doi:10.1515/mgmc.1999.22.8.497

Cited by 5 publications

(6 citation statements)

References 7 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)« Ksupporting

confidence: 58%

“…In the same way as for uncatalyzed similar reactions [11], one can conclude that the order with respect to alcohol depends on the association state of this reactant and corresponds to different pre-reaction complexes reacting in the rate determining step and composed of isocyanate, Sn(IV)alkoxide and of alcohol and /or solvent molecule(s).…”

Section: Resultsmentioning

confidence: 62%

“…The results can be discussed in the light of previous works concerned with catalyzed [8] and noncatalyzed [11] isocyanate -alcohol similar reactions. The latter in particular pointed out that solvent and/or alcohol molecules enter pre-reaction complexes (scheme 2) and so assist the formation of the activated complex of the determining step (eq.…”

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

confidence: 67%

“…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%

“…AaScri ti le 25°C scheme 2: proposed pre-reaction scheme 3: proposed structure of pre-reaction complexes in the uncatalyzed reaction [11]. complexes in the catalyzed reaction.…”

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

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)« Ksupporting

confidence: 58%

Section: Resultsmentioning

confidence: 62%

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

confidence: 67%

Section: Methodsmentioning

confidence: 99%

“…AaScri ti le 25°C scheme 2: proposed pre-reaction scheme 3: proposed structure of pre-reaction complexes in the uncatalyzed reaction [11]. complexes in the catalyzed reaction.…”

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

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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Investigations of catalysis of urethane formation using organotin dicarboxylate

Devendra

Edmonds

Söhnel

2020

Heliyon

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The reaction mechanism of the urethane formation for both aliphatic and aromatic isocyanates in the presence of organotin dicarboxylate as a catalyst is investigated theoretically and experimentally. Modelling on a dispersion corrected DFT level of theory (B3LYP-D3) shows that an alkoxide complex is formed between organotin dicarboxylate and alcohol. This complex is the dominant catalyst for the urethane formation reaction. In this study, the interaction between the alkoxide complex and isocyanate through N-coordination is considered. By using thermochemical data, it is possible to show that aliphatic isocyanates can be more sensitive to the carboxylic ligand content of the organotin compound as a catalyst in urethane formation in non-polar solvents compared to aromatic isocyanates. The interactions of carboxylic acid, which is formed as an intermediate in the catalysis process, with isocyanate and the effects on the catalytic process are also discussed.

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