Rule 2:Numbering the Main Chain Number the longest chain beginning at the end of the chain nearest a substituent. CH methy CH -CH2 CH CH ethyl CH- CH CHCH; CH-CH CH.CH: CH: CH CH3 CH CH CH, CH; methyl CH, methyl) incorrect correct 3-ethyl-2,4,5-trimethylheptane e20o的Eaon.能 2013 Pearson Education,Inc. Chapter 3 14© 2013 Pearson Education, Inc. • Number the longest chain beginning at the end of the chain nearest a substituent. Rule 2: Numbering the Main Chain Chapter 3 14