STRUCTURE AND PREPARATION OF ALKENES ELIMINATION REACTIONS

1 (b) Writing the structure in more detail, we see that the longest continuous chain contains four 

The double bond is located at the end of the chain, and so the alkene is named as a derivative of 1-butene. Two methyl groups are substituents at C-3. The correct IUPAC name is 3,3-dimethyl- 1 -butene. 

2 There are three sets of nonequivalent positions on a cyclopentene ring, identified as a, b, and c on the cyclopentene structure shown  

there are three different monochloro-substituted derivatives of cyclopentene. The carbons that bear the double bond are numbered C-l and C-2 in each isomer, and the other positions are numbered in sequence in the direction that gives the chlorine-bearing carbon its lower locant. 

3 (b) The alkene is a derivative of 3-hexene regardless of whether the chain is numbered from 

1 The El Mechanism for Acid-Catalyzed Dehydration of tert-Butyl Alcohol 203 

ALKENES are hydrocarbons that contain a carbon-carbon double bond. A carbon-carbon double bond is both an important structural unit and an important functional group in organic chemistry. The shape of an organic molecule is influenced by its presence, and the double bond is the site of most of the chemical reactions that alkenes undergo. 

This chapter is the first of two dealing with alkenes it describes their structure, bonding, and preparation. Chapter 6 examines their chemical reactions. 

We give alkenes lUPAC names by replacing the -ane ending of the corresponding alkane with -ene. The two simplest alkenes are ethene and propene. Both are also well known by their common names ethylene and propylene. 

The longest continuous chain that includes the double bond forms the base name of the alkene, and the chain is numbered in the direction that gives the doubly bonded carbons their lower numbers. The locant (or numerical position) of only one of the doubly bonded carbons is specified in the name it is understood that the other doubly bonded carbon must follow in sequence. The locant may precede the parent chain (1979 lUPAC rules) or the -ene suffix (1993 and 2004 recommendations). 

CHAPTER FIVE Structure and Preparation of Alkenes Elimination Reactions 

Ethylene is an acceptable synonym for ethene in the lUPAC system. Propylene, isobutylene, and other common names ending in -ylene are not acceptable lUPAC names. 

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