1 (473)

Prévia do material em texto

Chapter 21 Organic Chemistry 473 21.65 Given: disubstituted benzene structures Find: name Conceptual Plan: Consider the branches from the benzene ring to be substituents. Name the substituent according to Table 21.6 or using the base name of a halogen with an added at the end. Number the benzene ring start- ing with the substituent that is first alphabetically and count in the direction that gets to the second substituent with the lower position number. Write the name of the compound in the following format: (name of substitu- ent)benzene. List them alphabetically with hyphens between words and numbers. If a compound has two identical substituents, designate the number of identical substituents with the prefix di- (2) before the substituent's name. Separate the numbers with a comma, indicating the positions of the substituents relative to each other. Alternative names are 1,2 = ortho or o; 1,3 = meta or m; and 1,4 = para or p replacing the numbers. Solution: (a) Both of the substituent groups are Br or bromo groups. Start by giving one bromo an assignment of 1 and count in either direction to give the second bromo group an assignment of 4. The name is 1, 4-dibromobenzene or p-dibromobenzene. (b) Both of the substituent groups are CH₂CH₃ or ethyl groups. Start by giving the top ethyl an assignment of 1 and count in a clockwise direction to give the second ethyl group an assignment of 3. The name is 1,3-diethylbenzene or m-diethylbenzene. (c) One substituent group is or chloro, and the other is F or fluoro. Start by giving the chloro group an assignment of 1 and count in a counterclockwise direction to give the fluoro group an assignment of 2. The name is or o-chlorofluorobenzene. 21.67 Given: substituted benzene names Find: structures Conceptual Plan: Start with a benzene ring. Identify the structure of the substituent(s) according to Table 21.6 or using the base name of a halogen with an 0 added at the end. If only one substituent is present, simply at- tach it to the benzene ring. If a compound has two identical substituents, they are designated with the prefix di- (2) before the substituent's name. If there are two substituents, place the first one on the benzene ring and count clockwise around the ring to determine where to attach the second substituent. Note: 1,2 = ortho or o; 1,3 = meta or m; and 1,4 = para or p replacing the numbers. Solution: (a) isopropylbenzene. The isopropyl group is CH CH₃. Attach this to a benzene ring to make CH₃ CH₃ (b) meta-dibromobenzene. There are two bromo or - Br groups. The positions are 1 and 3 because the designation is meta. Attach the Br groups at the first and third positions to make Br Br. (c) One substituent group is - or chloro, and the other is CH₃ or methyl. Start by giving the chloro group an assignment of 1 and count in a clockwise direction to give the methyl group an assignment of 4. Attach the two groups to make CH₃. Copyright © 2017 Pearson Education, Inc.