Chemistry! ! ! 1. which of the following hydrocarbons must be an alkane? a. c2h2 b. c5h10 c. c7h12 d. c14h30 2. which of the following compounds cannot have different isomers? a. c7h16 b. c5h10 c. c3h8 d. c6h12o6 3. examine the following structural formula: (attached) the correct name for this compound is a. 2,2-dimethylbutane. b. 1,1,1-trimethylpropane. c. 2-ethyl-2-methylpropane. d. 3,3-dimethylbutane.

1. Identifying alkanes

d. C₁₄H₃₀

Explanation:

The general formula of an alkane is , where n is the number of C atoms.

If n = 14, 2n+2 =30. This compound is an alkane

a. is wrong. 2n+2 = 6. There is a deficiency of four H atoms.

b. is wrong. 2n+2 = 12. There is a deficiency of two H atoms.

c. is wrong. 2n+2 = 16. There is a deficiency of four H atoms.

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2. Identifying isomers

a. C₃H₈

Explanation:

A 3-carbon alkane is too short to have isomers. The smallest alkane that can have isomers has four carbon atoms.

Thus a. (9 isomers), b. (3 isomers) and d. (many isomers!) are all wrong.

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3. Naming alkanes

a. 2,2-Dimethylbutane.

Explanation:

1. Identify and name the longest continuous chain of carbon atoms (the main chain has 4 C; ∴ base name = butane).

2. Identify and name all the substituents [two 1C substituents (methyl)].

3. Number the main chain from the end closest to a substituent.

4. Identify the substituents by the number of the C atom on the main chain. Use hyphens between letters and numbers (2-methyl).

5. When there is more than one substituent of the same type, identify each substituent by its locating number and use a multiplying prefix to show the number of each substituent. Use commas between numbers (2,2-dimethyl).

6. Put the names of the substituents in front of the base name with no spaces. The name is 2,2-dimethylbutane.

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