烷烃的通式CnH2n+2
n=n1+n2+n3+n4
又因为伯、仲、叔、季四种碳原子分别连有3 2 1 0 个氢原子.有:
2n+2=3n1+2n2+n3
由两个式子消去n,可得:
n1=n3+2n4+2