Cycloalkenes physical properties

Structural isomers of alkynes have different physical properties. Alkynes, alkadienes and cycloalkenes containing the same number of carbon atoms are isomers of each other. 

There is little difference in physical properties between the alkenes and their saturated relatives, the alkanes. The odors of the alkenes are a bit more pungent and perhaps justify being called evU-smelling. Tn fact, the old trivial name for alkenes, olefins, readily evokes the sense of smell. Tables 3.2 and 3.3 list some data for alkenes and cycloalkenes. 

In this review, we will concentrate on the E-Z-photoisomerization and subsequent (photo)chemical transformations of cycloalkenes caused by direct and sensitized excitation. Valence isomerization, rearrangement, and fragmentation, observed upon irradiation of cyclopropene, cyclobutene, and cyclopen-tene, are only briefly described, as they have been extensively reviewed elsewhere. - - - Although the photochemistry of acycKc alkenes will not be included in this chapter, we will refer to the photobehavior of conjugated cycloalkenes, such as cycUc dienes, enones, and styrenes, as far as it relates to the cycloalkene functionahty. As the photochemical formation of labile (E)-cycloalkenes is one of the major topics in this chapter, the physical properties of the (E)-isomers will be tabulated and discussed in detail. Recent studies on enantiodifferentiating photoisomerization of cycloalkenes are summarized in one section in view of the rapidly growing interest in asymmetric photochemistry. ... 

Cycloalkene Physical and (Chir)optical Properties ds-Isomer trans-isomer Ref. 

Highly constrained (E)-cycloalkenes, generated readily through the photoisomerization of (Z)-isomers, are known to possess unique physical and (chir)optical properties. These properties are of particular interest and importance from both the experimental and theoretical points of view. For example, the experimental barriers of thermal E-to-Z isomerization of cycloalkenes are compared with the theoretical values obtained by semiempirical calculations. Among the calculations reported, the PM3 method appears to give good fits to the experimental results e.g., the experimental strain energy of (Z)-cyclooctene (20Z) is 11.37 kcal/mol, which is close to the value (10.55 kcal/mol) obtained by PM3. The relevant experimental (chir)optical properties, such as specific rotations and absorption maxima and thermodynamic parameters for isomerization, are summarized in Table 16.2. 

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