Química Orgânica: Isomeria e Reações

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Chapter 21 Organic Chemistry 481 CH₃ CH₂ CH₃ (d) The molecule contains a triple bond, it is an alkyne. The longest CH₃ carbon chain is 6. The prefix for 6 is hex-, and the base name is hexyne. The substituent groups are two CH₃ CH₂ CH₃ methyl groups and an ethyl group. If we start numbering the CH₃ chain at the end closest to the triple bond, the triple bond is between position numbers 1 and 2, the methyl sub- stituents are assigned numbers 3 and 5, and the ethyl substituent is assigned number 4. Because e comes before m, the name of the compound is 4-ethyl-3,5-dimethyl-1-hexyne. 21.93 (a) These structures are structural isomers. The methyl and ethyl groups have been swapped. (b) These structures are isomers. The second iodo group has been moved. (c) These structures are the same molecule. The first methyl group is simply drawn in a different orientation. 21.95 Given: 15.5 kg 2-butene hydrogenation Find: minimum g of H₂ gas Conceptual Plan: Write a balanced equation kg g mol mol g 1000 1 mol 1 mol H₂ 2.02 g H₂ 56.10 g 1 mol 1 mol H₂ Solution: then Check: The units (g) are correct. The magnitude of the answer (600) makes physical sense because we are reacting 15,500 g of butane. Hydrogen is lighter, and the molar ratio is 1:1; so the amount of hydrogen will be significant but less than the mass of butene. 21.97 (a) Combustion with oxygen to form CO₂ and H₂O (b) Alkane (halogen) substitution-reaction with halogen gas to substitute a hydrogen with a halogen (c) Alcohol elimination-ROH reaction with concentrated acid to eliminate water from the alcohol to produce an alkene (d) Aromatic (halogen) substitution-benzene reaction with halogen gas to substitute a hydrogen with a halogen 21.99 Given: alkene names Find: structure Conceptual Plan: Find the number of carbon atoms corresponding to the prefix of the base name in Table 21.5. Draw the base chain and number the carbons from left to right. Place the double bond in the appropriate position in the chain. Using Table 21.6 and the prefix di- (2), tri- (3), or tetra- (4) before the substituent's name, determine each substituent. Add the substituent to the proper carbon position in the chain. Add hydrogen atoms to the base chain that each carbon has four bonds. Look for substitutions around double bonds to de- termine whether cis-trans isomerism is applicable and look for carbons with four different alkyl groups attached. Solution: (a) 3-methyl-1-pentene. The base name pentene designates that there are five carbon atoms in the base chain. The -ene ending designates that there is a double bond, and the 1 prefix designates that it is between the first and second positions. 3-methyl designates that there is CH₃ a CH₃ group in the third position. Add hydrogens to the base chain to get the final CH₃ molecule There is optical stereoisomerism because the third carbon has four different groups attached. Copyright © 2017 Pearson Education, Inc.