Preparation of Alkenes Elimination Reactions

Chapter 5 Structure and Preparation of Alkenes Elimination Reactions 

Place a double bond in the carbon skeleton shown so as to represent 

Sample Solution (a) and (b) Because the methyl group must be at C-1, there are only two possible places to put the double bond  

In the Z stereoisomer the two lower priority substituents— the methyl group and the hydrogen—are on the same side of the double bond. In the E stereoisomer these substituents are on opposite sides of the double bond. The ring carbons are the higher ranking substituents at each end of the double bond. 

The rest of this chapter describes how alkenes are prepared by elimination that is, reactions of the type  

A quote from a biochemistry text is instructive here. This is not an easy reaction in organic chemistry, it is, however, a very important type of reaction in metaboiic chemistry and is an integrai step in the oxidation of carbohydrates, fats, and severai amino acids. G. L. Zubay, Biochemistry, 

Alkene formation requires that X and Y be substituents on adjacent carbon atoms. By making X the reference atom and identifying the carbon attached to it as the a carbon, we see that atom Y is a substituent on the 3 carbon. Carbons succeedingly more remote from the reference atom are designated y, 8, and so on. Only p elimination reactions will be discussed in this chapter. [Beta O) elimination reactions are also known as 1,2 eliminations.] 

You are already familiar with one type of p elimination, having seen in Section 5.1 that ethylene and propene are prepared on an industrial scale by the high-temperature dehydrogenation of ethane and propane. Both reactions involve p elimination of H2. 

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