The thermal decomposition of <i>t</i>-alkyl <i>N</i>-arylcarbamates. I. The effect of ring substituents

Thorne, Melanie P.

doi:10.1139/v67-415

Cited by 29 publications

(21 citation statements)

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“…Analyses for residual amine and urea were carried out by the methods described previously (1). The potentiometric titrations of the amine with hydrochloric acid in the 1 :1 ethylene glycol-isopropanol solvent mixture were done automatically using Radiometer Automatic Titration Equipment.…”

Section: A~nine and Urea Analysesmentioning

confidence: 99%

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The Thermal Decomposition of N-Arylcarbamates of t-Alcohols. 2. Effects of Solvent, Temperature, and Substituents

Ashcroft¹,

Thorne²

1972

Can. J. Chem.

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The influence of solvent, ring substituents, and tertiary carbon atom substituents on the decomposition at 423–473 K of some N-arylcarbamates of tertiary alcohols (p-XC6H4NHCO2C(CH3)2R, where X = CH3, H, Cl, NO2, R=C≡CH, C2H5, CH=CH2) has been investigated. In dodecane, diphenyl ether, acetophenone, nitrobenzene, and decanol, the reactions were first order yielding chiefly carbon dioxide, amine, and olefin. t-Pentyl carbamates yielded the olefins 2-methyl-1-butene and 2-methyl-2-butene in a 3:1 mixture. Solvent effects are reflected in variations in enthalpies and entropies of activation, but effects on the actual values of the specific rate constants are small. Substituent effects are also small, with changes in R from C≡CH to CH=CH2 producing only a tenfold rate increase. Variations in X yield Hammett σρ plots with slopes of about 0.50. These results are consistent with the charge separated cyclic transition state proposed before (1). In ethylene glycol, increased reaction rates and 1:1 yields of the olefins from the t-pentyl carbamates indicate a mechanism with greater carbonium ion character.

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Section: A~nine and Urea Analysesmentioning

confidence: 99%

“…Introduction N-Phenylcarbamates and meta or para substituted N-phenylcarbamates of l-butanol have been shown previously (1) to decompose in diphenyl ether at 450 K according to eq. 1.…”

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confidence: 99%

The Thermal Decomposition of N-Arylcarbamates of t-Alcohols. 2. Effects of Solvent, Temperature, and Substituents

Ashcroft¹,

Thorne²

1972

Can. J. Chem.

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“…Several studies [22][23][24][25] have regarded TPUs as undergoing two-stage degradations. The first stage degradation that occurs between 200 and 370 o C is a de-polycondensation process associated with urethane hard segment degradation.…”

Section: Introductionmentioning

confidence: 99%

Effect of hot pressing/melt mixing on the properties of thermoplastic polyurethane

et al. 2009

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In-depth understanding of the influence of hot pressing and melt processing on the properties of thermoplastic polyurethane (TPU) is critical for effective mechanical recycling of TPU scraps. Therefore, this study focused on the effects of hot pressing and melt mixing on molecular weight (MW), polydispersity index (PDI), melt index (MI), characteristic IR peaks, hardness, thermal degradation and mechanical properties of TPU. The original TPU pellet (o-TPU) showed two broad peaks at lower and higher MW regions. However, four TPU film samples, TPU-0 prepared only by hot pressing of o-TPU pellet and TPU-1, TPU-2 and TPU-3 obtained by hot pressing of melt mixed TPUs (where the numbers indicate the run number of melt mixing), exhibited only a single peak at higher MW region. The TPU-0 film sample had the highest M n and the lowest PDI and hardness. The TPU-1 film sample had the highest M w and tensile modulus. As the run number of melt mixing increased, the peak-intensity of hydrogen bonded C=O stretching increased, however, the free C=O peak intensity, tensile strength/elongation at break and average MW decreased. All the samples showed two stage degradations. The degradation temperatures of TPU-0 sample (359 o C and 394 o C) were higher than those of o-TPU (342 o C and 391 o C). While all the melt mixed samples degraded at almost the same temperature (365 o C and 381 o C). The first round of hot pressing and melt mixing was found to be the critical condition which led to the significant changes of M n /M w /PDI, MI, mechanical property and thermal degradation of TPU.

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“…These absorptions agree well with those reported for other N-substituted carbamates (3,(5)(6)(7). The proton chemical shifts for the nmr spectra of the rert-butyl carbamates have already been reported (9). Structural variations in the other carbamates gave the expected variations in the nmr spectra In all cases the H-N absorption appeared at about S = 6.5 ppm; frequently as a broad band.…”

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confidence: 59%

“…Their lower deco~nposition temperatures and ease of preparation offer advantages over acetates and xanthates which have been used previously (8). A kinetic study of the thermal degradation of the monocarbamates has already been reported (9,10).…”

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confidence: 99%

Carbamates and 2-oxazolidinones from tertiary alcohols and isocyanates

Francis¹,

Thorne²

1976

Can. J. Chem.

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The thermal decomposition of t-alkyl N-arylcarbamates. I. The effect of ring substituents

Cited by 29 publications

References 0 publications

The Thermal Decomposition of N-Arylcarbamates of t-Alcohols. 2. Effects of Solvent, Temperature, and Substituents

The Thermal Decomposition of N-Arylcarbamates of t-Alcohols. 2. Effects of Solvent, Temperature, and Substituents

Effect of hot pressing/melt mixing on the properties of thermoplastic polyurethane

Carbamates and 2-oxazolidinones from tertiary alcohols and isocyanates

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