Strained hydrocarbons, enhanced

This test uses specially constructed bacteria to detect reverse mutations. Each tester strain has enhanced sensitivity and selectivity for the classes of compounds it will pick up. Therefore, several tester strains are generally used to maximize the possibility of detecting a mutagenic compound. It is well known now that many compounds, for example polycyclic aromatic hydrocarbons, must undergo some kind of enzymatic or chemical modification before becoming reactive. Therefore, in many cases an enzyme preparation (commonly called S9) is added to the chemical in order to ensure conversion to a chemically-reactive species. 

The chemistry of the closest relative of hydrocarbon 1- methylenecyclopropane (2) - has recently been reviewed extensively [2]. The presence of the second three-membered ring in 1 strongly increases the total strain of this molecule, this enhances its chemical reactivity and leads to specific physical properties. The meanwhile large variety of experimental material obtained for compound 1, some of its derivatives and analogs prompted us to summarize the results in order to help set the stage for future developments. 

As discussed earlier in Sect. 5.3.3 of this review, because of the incremental strain imparted by fluorine substitutents to cyclopropane systems, the rate of ring-opening of the 2,2-difluorocyclopropylcarbinyl radical is substantially enhanced with respect to the already very fast analogous hydrocarbon system [174],... 

Further approaching and deforming the benzene rings by additional short bridges ought to enhance both of the peculiarities of [2.2]paracyclophane. The recently synthesized highly strained, multiply bridged phane hydrocarbons (e.g. 2,15,16,... 

Table 6.4 shows the principal photoreactions of aromatic compounds that we discuss in this chapter. Upon irradiation, aromatic compounds, such as benzenes, naphthalenes and some of their heterocyclic analogues, undergo remarkable rearrangements that lead to some non-aromatic highly strained products, such as benzvalene and Dewar benzene (entry 1), which can be isolated under specific conditions. Quantum and chemical reaction yields are usually low however, photochemistry may still represent the most convenient way for their preparation. While bulky ring substituents usually enhance the stability of those products, aromatic hydrocarbons substituted with less sterically demanding substituents exhibit ring isomerization (phototransposition) (entry 2). 

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