1 (482)

Prévia do material em texto

482 Chapter 21 Organic Chemistry (b) 3,5-dimethyl-2-hexene. The base name hexene designates that there are six carbon atoms in the base chain. The -ene ending designates that there is a double bond, and the 2 prefix designates that it is between the second and third CH₃ CH₃ designates that there are -CH₃ groups in the third and fifth positions. CH₃ CH₃ Add hydrogens to the base chain to get the final molecule CH₃ CH₂ CH₃. Cis-trans geometric isomerism is possible around the double bond because all of the groups surrounding the double bond are different. (c) 3-propyl-2-hexene. The base name hexene designates that there are six carbon atoms in the base chain. The -ene ending designates that there is a double bond, and the 2 prefix designates that it is between the second and third positions. designates that there is a group in the third position. Add hydrogens to the base chain to get the final molecule geometric isomerism is not possible around the double bond because the two groups on the third carbon are the same. 21.101 The 11 isomers are = aldehyde; ketone; = alcohol and alkene; CH₃ CH₂ OH = alcohol and alkene; CH₂ OH = alcohol and alkene; CH₃ CH₂ CH₂ = ether and alkene; CH₂ CH₂ = ether and alkene; CH₃ CH₃ = ether and alkene; OH OH = alcohol and alkene; = alcohol and alkene; and OH = alcohol and alkene. There is also a twelfth isomer that is cyclic: H₂C CH₂ = ether. 21.103 In the acid form of the carboxylic acid, electron withdrawal by the enhances acidity. The conjugate base, the carboxylate anion, is stabilized by resonance; so the two atoms are equivalent and bear the negative charge equally. This resonance stability is not possible in an alcohol, where the carbonyl group is absent. Challenge Problems 21.105 This is an internal condensation reaction. It requires only heat to cause it to happen. (a) C OH 0 + C OH Heat C 0 0 Copyright © 2017 Pearson Education, Inc.