Cycloalkenes and cycloalkadienes

Cycloalkenes and cycloalkadienes are about as reactive chemically as their open-chain analogs. Cycloalkenes can undergo addition reactions in which the double bond is eliminated and also can undergo cleavage reactions which cause the ring structure to be opened into a chain. 

Constrained (E)-isomers of medium-sized cycloalkenes and cycloalkadienes have long been known to be chiral and indeed the enantiomerically pure or enriched (I -cyclooctene/cyclooctadienes were resolved optically and/or synthesized via thermal reactions in the 1960s [26] photochemical preparation of ( )-cyclooctene from the (Z)-isomer was also reported in the late 1960s [27]. Nevertheless, the... 

Bischof, P. and Heilbronner, E., Photoelectron spectra of cycloalkenes and cycloalkadienes, Helv. Chim. Acta, 53, 1677-1682, 1970. 

Alicyclic Hydrocarbons. These refer to cyclic analogues of aliphatic hydrocarbons and are named accordingly, using the piefix cyclo-." Their properties are similar to their open-chain aliphatic counterparts. Alicyclic hydrocarbons are subdivided into monocyclic (cycloalkanes, cycloalkenes, cycloalkynes, cycloalkadienes, etc.) and polycyclic aliphatic compounds. Monocyclic aliphatic structures having more than 30 carbon atoms in the ring are known, but those containing 5 or 6 carbon atoms are more commonly found in nature [47, p. 28]. 

We thus have the families cycloalkanes, cycloalkenes, and cycloalkynes, as well as the multi-double and triple-bond variants such as cycloalkadienes and -atrienes, and cycloalkadiynes, -atriynes, etc. Naming the cyclo compounds corresponds to the naming of the straight-chain forms except that carbon atoms are numbered such that substituents are on the lowest numbered carbon atoms. This... 

Under the conditions which cause migration of the double bonds, e.g. treatment with sodium and especially potassium, the isolated double bonds can become conjugated, and thus they undergo reduction by metals. Some macrocyclic cycloalkadienes were reduced (predominently to trans cycloalkenes) by treatment with potassium on alumina in a hydrogen atmosphere [350]. 

Depending on the reaction conditions, alkenes may undergo either of two types of catalytic polymerization. The products of the first type, which may be termed true polymerization, consist of alkenes having molecular weights which are integral multiples of the monomer alkene. The second type, conjunct polymerization, yields a complex mixture of alkanes, alkenes, alkadienes, cycloalkanes, cycloalkenes, cycloalkadienes, and, in some cases, aromatic hydrocarbons the products do not necessarily have a number of carbon atoms corresponding to an integral multiple of the monomer. 

Exercise 15-43 Draw structures for the following compounds and name each as an oxa-, aza-,drthiacycloalkane (cycloalkene, cycloalkadiene, and so on, as appropriate). 

Mono- and dihalobicycloalkanes undergo direct thermal cleavage to give halocycloalkenes. In the presence of lepidine (4-methylquinoline), ring cleavage is accompanied by dehyd-rohalogenation to afford cycloalkadienes as the isolable products. /roHs-Cycloalkenes are not stable at the temperatures of these thermolyses and in each case only the cw-cycloalkene was obtained (Table 3). ... 

ENOLETHER/ /ISOL/ /0-FUNCT/ /CYLOHEXANE/ /CYCLOALKADIENE/ /AND/ /N-SULFONYL/ /AZIDE/ GIVES CYCLOPENTANE ISOL CYCLOALKENE IMINOESTER+ N-SULFONYL C-FUNCT RING-CONTRACTION,II ULTRASONIC PRESSURE=4 TEMP=4 SOLV=6... 

Complexes of structure (51) have been prepared by either reaction of HVfCO) with the cycloalkadiene or reaction of Na[V(CO) ] with a 3-halo-cycloalkene reaction with PPha yields both mono- and di-substituted derivatives. Syn-anti proton exchange in M( -allyl)4 and (cot)M( y -allyl)2 (M=Zr, Hf) probably occurs by a n-ya- 7i rearrangement activation energies are 6.5 and 11.4 kcal mol , respectively, where M = Hf and 15.2 and 9.1 kcal mol S respectively, where M = Zr. ... 

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