CI CH3 7 3 21 CH3 CHCHCH2C≡CHCH3 654 5-甲基6-氯-2-庚炔 CH3(CHz)5C≡CH 1-十八碳炔CH3CHCHCH2C CHCH3 Cl CH3 7 3 2 1 6 5 4 5-甲基-6-氯-2-庚炔 CH3(CH2)15C CH 1-十八碳炔