Chapter 5.2: Nomenclature of Alkenes

a prefix meaning across from

a -CH2 group

Z

specifies that groups of higher priority on the carbons of a double bond are on opposite sides

a -CH=CH2 group

a prefix meaning on the same side

o To form IUPAC names for alkenes, change the -an- infix of the parent alkane to -en- o According to the IUPAC System  Number the longest carbon chain that contains the double bond in the direction that gives that gives the carbon atoms of the double bond the lowest possible numbers  Indicate the location of the double bond by the number of its first carbon  Name branched or substituted alkenes in a manner similar to alkanes  Number the carbon atoms, locate and name substituent groups, locate the double bond, and name the main chain

steric strain in Z

a system to specify the configuration of groups about a carbon-carbon double bond

methylene

o For alkenes containing two or more double bonds, the infix -en- is changed to -adien-, -atrien-, and so on

E

o In naming cycloalkenes, the carbons atoms of the ring double bond are numbered 1 and 2 in the direction that gives the substituent encountered first the smaller number

E,Z system

trans

specifies that groups of higher priority on the carbons of a double bond are on the same side

E is more stable than Z

vinyl

allyl

• a -CH2CH=CH2 group

cis