Chapter 20

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There are several sets of answers; one is:
(a) C₅H₁₂

A chain of five C atoms with single bonds is shown. Each C atom has an H atom bonded above and below it. The C atoms on the end of the chain have a third H atom bonded to them each.

(b) C₅H₁₀

Both reactions result in bromine being incorporated into the structure of the product. The difference is the way in which that incorporation takes place. In the saturated hydrocarbon, an existing C–H bond is broken, and a bond between the C and the Br can then be formed. In the unsaturated hydrocarbon, the only bond broken in the hydrocarbon is the π bond whose electrons can be used to form a bond to one of the bromine atoms in Br₂ (the electrons from the Br–Br bond form the other C–Br bond on the other carbon that was part of the π bond in the starting unsaturated hydrocarbon).

Unbranched alkanes have free rotation about the C–C bonds, yielding all orientations of the substituents about these bonds equivalent, interchangeable by rotation. In the unbranched alkenes, the inability to rotate about the bond results in fixed (unchanging) substituent orientations, thus permitting different isomers. Since these concepts pertain to phenomena at the molecular level, this explanation involves the microscopic domain.

They are the same compound because each is a saturated hydrocarbon containing an unbranched chain of six carbon atoms.

(a) C₆H₁₄

This figure shows a horizontal hydrocarbon chain consisting of six singly bonded carbon atoms. Each C atom has an H atom bonded above and below it. The two C atoms on either end of the chain each of a third H atom bonded to it.

(b) C₆H₁₄

(d) C₆H₁₂

(e) C₆H₁₀

(f) C₆H₁₀

11.

(a) 2,2-dibromobutane; (b) 2-chloro-2-methylpropane; (c) 2-methylbutane; (d) 1-butyne; (e) 4-fluoro-4-methyl-1-octyne; (f) trans-1-chloropropene; (g) 4-methyl-1-pentene

13.

Two structures are shown. The first includes a chain of four singly bonded C atoms. Each C atom has two H atoms bonded above and below it. The two C atoms at either end of the chain each have a third H atom bonded to it. The molecule is named n dash butane. The second includes a chain of three singly bonded C atoms with a C atom bonded above the middle C atom in the chain. The first C atom (from left to right) has three H atoms bonded to it. The second C atom has one H atom bonded below it and a C atom bonded above it. The C atom bonded above the middle C atom has three H atoms bonded to it. The third C atom in the chain has three H atoms bonded to it. This molecule is named 2 dash methylpropane.

15.

This figure includes two structural formulas. The first structure shows two double bounded C atoms with C l bonded to the upper right, C H subscript 3 bonded to the upper left, and H atoms attached to the lower right and lower left in the structure. This structure is labeled cis dash. The second structure shows two double bounded carbon atoms with C l attached to the lower right, C H subscript 3 attached to the upper left, and H atoms attached to the upper right and lower left in the structure. This structure is labeled trans dash.

17.

(a) 2,2,4-trimethylpentane; (b) 2,2,3-trimethylpentane, 2,3,4-trimethylpentane, and 2,3,3-trimethylpentane:

19.

Four structural formulas are provided. The first has a hydrocarbon chain with a length of four C atom. All bonds are single. Nine H atoms are attached and a single C l atom is attached at the far right end of the structure which is labeled 1 dash chlorobutane. The second has a hydrocarbon chain with a length four C atoms. All bonds are single. Nine H atoms are attached and a single C l atom is attached above the second carbon counting left to right. This structure is labeled 2 dash chlorobutane. The third has a hydrocarbon chain with a length of three C atoms. All bonds are single. A single C l atom is bonded beneath the middle C atom and a C H subscript 3 group is also bonded above the middle C atom. Six H atoms are attached, and the structure is labeled 2 dash chloro dash 2 dash methylpropane. The fourth structure has a hydrocarbon chain with a length of three C atoms. All bonds are single. A single C l atom is bonded beneath the first C atom (from left to right) and a C H subscript 3 group is bonded above the middle C atom. Six H atoms are attached, and the structure is labeled 1 dash chloro dash 2 dash methylpropane.

21.

In the following, the carbon backbone and the appropriate number of hydrogen atoms are shown in condensed form:

23.

Two structural formulas are shown. The first shows two C atoms with a triple bond between them. At each end of the structure, a single H atom is bonded. The second structure involves a hydrocarbon ring of 6 C atoms with a circle at the center. There are alternating double bonds between C atoms. Each C atom is bonded to a single H atom.

In acetylene, the bonding uses sp hybrids on carbon atoms and s orbitals on hydrogen atoms. In benzene, the carbon atoms are sp² hybridized.

25.

(a)

(b)

27.

65.2 g

29.

9.328 10² kg

31.

(a) ethyl alcohol, ethanol: CH₃CH₂OH; (b) methyl alcohol, methanol: CH₃OH; (c) ethylene glycol, ethanediol: HOCH₂CH₂OH; (d) isopropyl alcohol, 2-propanol: CH₃CH(OH)CH₃; (e) glycerine, l,2,3-trihydroxypropane: HOCH₂CH(OH)CH₂OH

33.

(a) 1-ethoxybutane, butyl ethyl ether; (b) 1-ethoxypropane, ethyl propyl ether; (c) 1-methoxypropane, methyl propyl ether

35.

HOCH₂CH₂OH, two alcohol groups; CH₃OCH₂OH, ether and alcohol groups

37.

(a)

(b) 4.593 10² L

39.

(a)

(b)

41.

(a)

A molecular structure is shown with a C H subscript 3 group bonded up and to the right to a C H subscript 2 group which is bonded down and to the left to a C atom. This C atom appears in red. The C atom forms a double bond with an O atom up and to the right. The C atom also forms a single bond with an O H group directly below it.

(b)

A molecular structure is shown with a C H subscript 3 group bonded up and to the right to a C H subscript 2 group which is bonded down and to the left to a C group. This C atom appears in red. The C atom forms a double bond with an O atom up and to the right. Directly below the C atom is a single bond to an H atom.

(c)

A molecular structure is shown with a C H subscript 3 group which is bonded up and to the right to a C H subscript 2 group. The C H subscript 2 group is bonded down and to the left to an C atom. This C atom appears in red. The C atom forms a double bond with an O atom up and to the right. The C atom also forms a single bond to a C H subscript 3 group which appears directly below it.

43.

A ketone contains a group bonded to two additional carbon atoms; thus, a minimum of three carbon atoms are needed.

45.

Since they are both carboxylic acids, they each contain the –COOH functional group and its characteristics. The difference is the hydrocarbon chain in a saturated fatty acid contains no double or triple bonds, whereas the hydrocarbon chain in an unsaturated fatty acid contains one or more multiple bonds.

47.

(a) CH₃CH(OH)CH₃: all carbons are tetrahedral; (b) the end carbons are tetrahedral and the central carbon is trigonal planar; (c) CH₃OCH₃: all are tetrahedral; (d) CH₃COOH: the methyl carbon is tetrahedral and the acid carbon is trigonal planar; (e) CH₃CH₂CH₂CH(CH₃)CHCH₂: all are tetrahedral except the right-most two carbons, which are trigonal planar