stylistic:tone, structural:scholar_edition, information:highlighting
Alkenes

Alkenes are named for their parent alkane chain with the suffix " -ene " and a numerical root indicating the position of the carbon with the lower number for each double bond in the chain: CH =CHCH CH is but-1-ene.Multiple double bonds take the form -diene, -triene, etc., with the size prefix of the chain taking an extra "a": CH =CHCH=CH is buta-1,3-diene. Simple cis and trans isomers may be indicated with a prefixed cis- or trans-: cis -but-2-ene, trans -but-2-ene. However, cis- and trans- are relative descriptors. It is IUPAC convention to describe all alkenes using absolute descriptors of Z- (same side) and E- (opposite) with the Cahn–Ingold–Prelog priority rules (see alse E–Z notation).