Cyclohexadiene, from benzene

Miscellaneous.- New optically active phosphites (103) and (104) derived from R- or 5-2,2 -binaphthol have been prepared by standard methods and used as ligands for asymmetric hydroformylation or hydrocyanation reactions. Low to moderate asymmetric induction was achieved in the synthesis of S,6-disubstituted cyclohexadienes from benzene chromium complexes when the optically active phosphites (105) were ligands. ... 

Lithium/ethylamine/tert-amyl alcohol 1,4-Cyclohexadiene from benzene ring with subsequent migration of carbon-carbon doubie bonds... 

Thus, heterobifunctional cyclohexadienes are accessible from benzene by temporary complexation to Fe2+ which reverses the reactivity of the aromatic. Double nucleophilic attack is possible but only using protection-deprotection by hydride. 

The adsorption of cyclohexene, cyclohexane, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and benzene on Pt(l 11) was studied with STM [35, 36]. Figure 7.20a shows an STM image of 2 x 10-s Torr cyclohexene on Pt(l 11). The low-pressure structure shows a hexagonal symmetry with a periodicity of approximately 7 A that is rotated approximately 18-20° with respect to the [1 1 0] direction of the Pt crystal face. From prior... 

Probtom 10.3 (a) Use the AH s for complete hydrogenation of cyclohexene, 1,3-cyclohexadiene and benzene, as given in Problem 10.2, to calculate for the addition of 1 mole of Hj to (i) 1,3-cyclohexadiene, (ii) benzene, (b) What conclusion can you draw from these values about the rate of adding 1 mol of Hj to these three compounds (The AH of a reaction step is not necessarily related to AH of the step. However, in the cases being considered in this problem, is directly related to AH. ) (c) Can cyclohexadiene and... 

Dehydrogenation catalysts.2 Reduction of di(benzene)chromium with potassium sand in DME generates a species that dehydrogenates 1,4-cyclohexadiene to benzene. The catalyst prepared from benzene(l,3-cyclohexadiene)iron(0) promotes dehydrogenation and disproportionation to cyclohexene and benzene. 

Irradiation of 1,3,5-hexatriene (81) in the vapor phase leads to the formation of 1,3-cyclohexadiene (82), benzene, hydrogen, and 1,2,4-hexatriene (83), in addition to a liquid polymer 63>. Determination of the quantum yield 64> led to the conclusion that 83 may originate from an electronically excited molecule, while benzene and hydrogen occur from a vibrationally excited ground state molecule (1,3-cyclohexadiene) formed by internal conversion from the electronically excited molecule. 

The pioneering work of Gibson3 on the isolation and mutation of Pseudomonas strains that oxidatively degrade aromatic compounds has led, 25 years later, to the application of cyclohexadiene cis-diols in asymmetric synthesis. The first applications of these types of compounds to synthesis were the use of meso-diol derived from benzene for production of polyphenylene4 by ICI and in the synthesis of racemic... 

Marked decreases of the primarily formed butenes and butadiene with ethylene conversion suggest that these olefins play an important role forming secondary products. In fact, subsequent experiments showed that the addition of butadiene, 3-5 mole %, to ethylene accelerates the formation of cyclopentene, cyclohexene, cyclohexadiene, and benzene (Table I). It seems reasonable, therefore, to propose the following reaction scheme for the formation of cyclic compounds from olefins. 

In Figure 16, conversions of butadiene at temperatures from 550° to 750°C are plotted, and a second-order rate equation is shown to hold. Here, the conversion of butadiene, x, is defined as twice the sum of the yields of 4-vinylcyclohexene, cyclohexene, cyclohexadiene, and benzene. 

The yield of labeled benzene can be enhanced by the presence of the benzene-iodine complex during irradiation. Pozdeev et al. (1962a) ascribe this effect to stabilization of a highly excited intermediate which results in increased probability of hydrogen loss from the intermediate. Phase-effect studies on cyclohexane, cyclohexene, cyclohexadiene and benzene by Pozdeev et al. (1962b) lend further support to the excited-... 

From Figure 1, it is clear that the primary products of the thermal reaction of diallyl are ethylene, propylene, 1-butene, butadiene, 1-pentene, cyclopentene, cyclopentadiene, and 1,3,5-hexatriene, and the secondary products are 1,3-cyclohexadiene and benzene. Trace amounts of methane, propane, and 1,4-pentadiene were also found in some experiments. No hydrogen was detected by a nitrogen carrier gas chromatograph with MS 5A column. The formation of C 2 compounds was noticed at low temperatures. A small amount of liquid product was found in the separator tube after 50 or more experimental runs. The average molecular weight of the liquid product was 428 based on the method of Hill (15). 

The Ir complex is able to abstract H atoms from cyclohexadiene and slowly from cyclohexene but not from isopropylbenzene. The final products from cyclohexadiene are benzene and Ir2H2, for which v(Ir-H) is seen at 1940 cm l. The rate of the initial H atom abstraction was shown to increase as the C-H bond energy of the substrate decreases. 

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