The article contains sections titled: 1. Introduction 1.1. Market and Areas of Application 1.2. Nomenclature and Classification 1.3. Properties 1.4. Production 1.5. Producers 2. Market, Producers, and Capacities 2.1. Market 2.2. Producers, Capacities and Capacity Utilization 3. Market Requirements and Impact on Development of Synthetic Rubber 4. Production Processes 5. Ecological and Health Aspects 5.1. Introduction 5.2. Health Aspects 5.2.1. Raw Materials 5.2.2. Processing 5.2.3. Use 5.3. Environment 5.4. Outlook

The title study has been carried out in the temperature range 210-250°C. The isomerisation products are 2-butyne (91 -94%), 1,3-butadiene (5-8%), and 1,Zbutadiene (1 -2%). No other products were detected and material recovery was complete within experimental error (+ 5%). The reaction obeyed first-order kinetics, with the products formed by parallel pathways, and appeared to be both unimolecular and homogeneous although some surface sensitivity was detected in packed vessels. Studies of pressure dependence showed characteristic rate constant "fall-off' below 20 Torr (SF,) and 100 Torr (Nz). Within at least 2% of the high pressure limit, the following Arrhenius equation for overall decomposition wasArrhenius equations were similarly found for the individual pathways. The figures are discussed in the light of Transition State Theory and represent a significant improvement over a previous study. It is argued that all products arise via 1,2-H shifts in a diradical-like intermediate and the propensities for different H shifts are discussed. A 1 -methyl substituent, rather surprisingly, deactivates cyclopropene in its isomerisation reactions. Die Gasphasenkinetik der Pyrolyse yon 1-Methyl-1-cyclopropn')Die Pyrolyse von I-Methyl-I-cyclopropen wurde im Temperaturbereich von 210 -250 "C untersucht. Als Isomerisierungsprodukte wurden 2-Butin (91 -94%), 1,3-Butadien (5 -8%) und 1,2-Butadien (1 -2%) nachgewiesen; andere Produkte entstehen bei vollstandiger Materialbilanz ( * 5% Abweichung vom berechneten Wert) nicht. Die Reaktion verlauft nach einem Zeitgesetz 1. Ordnung, wobei die isomeren Produkte in parallelen Reaktionswegen gebildet werden. Die Umlagerungen erfolgen unimolekular und homogen, obwohl in gepackten ReaktionsgefaDen eine gewisse Oberflachenabhangigkeit beobachtet wurde. Charakteristisches "fall-off'-Verhalten tritt in Gegenwart von SF6 unterhalb von 20 Torr, in Gegenwart von N2 unterhalb von 100 Torr ein. Die Gesamtreaktion laBt sich innerhalb des Hochdruckbereichs durch die folgende Arrhenius-Gleichung beschreiben:

The pyrolysis of 12-dimethylcyclopropene has been studied in the temperature range 260-300 "C. The sole product is isoprene and material recovery was complete to within 3.5%. The reaction obeyed firstorder kinetics and appeared to be homogeneous in a hexamethyldisilazane-conditioned Pyrex reactor, although surface catalysis could not be eliminated in a packed vessel. At 12 Torr (close to the highpressure limit) rate constants fitted the Arrhenius equation (i). This study provides further evidence for the log(k/s-') = (1 3.63 & 0.1 9) -(1 83.7 & 2.0 kJ mol-')/RTlnlO (0 deactivating effect of methyl substituents on cyclopropene isomeritation.

Tknnrl R aw XVIIi'? -GWJ P~w pyroly~is Of C Y C b P r o P Y~t ) .~The gas phase pyrolysis of cyclopropylacetylene (3) has been investigated in a flow system between 600 and 900°C. At the lower temperature limit 3 isomerizes to give 12,4pentatriene (9), cis-(10) and tram-3-penten-I-yne (ll), as well as 1-pentenCyne (12), all isomers being formed in roughly equal amounts. Bei 600°C besteht das Pyrolysat laut GC-Analyse zu 35% aus Edukt, sowie den vier acyclischen C5H6-Isomeren 1,2,4-Pentratrien (9, Vinylallen), cis-(10) und trans-3-Penten-I-in (1 1) und 1-Penten-4-in (12 Chem.

1 -Ethynyl-2,2,3,3-tetramethylcyclopropane (9) has been prepared and subjected to gas phase pyrolysis. Above 200°C the hydrocarbon rearranges to 4,4,5-trimethyl-I ,2,5-hexatriene (10) and 5,6-dimethyl-5-hepten-I-yne (11). Whereas the allene is produced directly from 9 by a 1,Shydrogen shift, the alkyne is a secondary product formed from 10 by a [3,3] sigmatropic rearrangement.The activation parameters (Ea, Ig A) for both processes have been determined for the 210 to 250°C temperature range. The data are discussed and compared with those for other concerted reactions of alkynes and alkenes.Thermal reactions of acetylenic hydrocarbons have received growing attention in recent years'-4), and many studies have shown that these processes are chemically as varied and preparatively as useful as those of their olefinic counterpart^^-^). In contrast to these latter systems kinetic data for acetylenic molecules are conspicously lacking''. A comparison between the two classes of hydrocarbons aimed at elucidating the effect caused by replacement of a double bond by the geometrically distinctly different triple bond group is thus hampered. A case in point is provided by cis-I-ethenyl-2-methylcyclopropane (1) and cis-1 -ethynyl-2-methylcyclopropanc (3). respectively. Whereas the former molecule, which on heating undergoes a homodienyl-1,s-hydrogen shift -leading to cis-1,4-hexadiene (2) -has been investigated in great detail*', only qualitative results (i.e. a product study) are available for the thermal behavior of 3. In our first experiments we found that the alkyne also suffers a 1,s-hydrogen shift providing 1,2,5-hexatriene (4) as the initial product. The allene undergoes subsequent isomerization reactions", for example a ring closure that begins with the formation of diradical 5 which, in turn, may stabilize itself by 1,2-hydrogen shifts.Since our initial work9' the parent molecule has been investigated (qualitative study of its high-temperature gas phase pyrolysis". In addition, the thermal isomerization of various acetylenic epoxides has been developed by Dreiding and co-workers into a valuable method for chain and ring extension"'. Moreover, as part of an investigation of the trimethylene methane energy surface, Berson and his coworkers have studied briefly the pyrolysis of l-ethynyl-2,2,3-trimethylcyclopropane 'I). Once again there is good evidence for the occurrence of a 1,s-hydrogen shift.All this work has been qualitative, and the determination of reliable kinetic data has hence become highly desirable.We report here a detailed study of the gas phase pyrolysis of 1-ethynyl-2,2,3,3-tetramethylcyclopropane (9). This hyChem.