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Explain why unbranched alkenes can form geometric isomers while unbranched alkanes cannot. Does this explanation involve the macroscopic domain or the microscopic domain?

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 C = C 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.

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Explain why these two molecules are not isomers:
Two structural formulas are shown. In the first, a chain of six carbon atoms with a single double bond between carbons two and three counting right to left across the molecule is shown with twelve total H atoms bonded. H atoms are bonded at each end of the molecule as well as above. H atoms are also bonded below all C atoms except those involved in the double bond. In the second structure, a hydrocarbon chain of five C atoms connected by single bonds is shown. A single C with three attached H atoms is bonded beneath the second carbon counting right to left across the molecule.

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Explain why these two molecules are not isomers:
Two structural formulas are shown. In the first, a horizontal hydrocarbon chain consisting of six singly bonded C atoms is shown. Each C atom has an H atom bonded above and below it. The two C atoms on either end of the chain each have a third H atom bonded to them. In the second structure, a horizontal hydrocarbon chain composed of five C atoms connected by single bonds is shown with a sixth C atom singly bonded beneath the right-most C atom. The first C atom (from left to right) has three H atoms bonded to it. The second C atom has two H atoms bonded to it. The third C atom has two H atoms bonded to it. The fourth C atom has two H atoms bonded to it. The fifth C atom has two H atoms bonded to it. The C atom bonded below the fifth C atom has three H atoms bonded to it.

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

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How does the carbon-atom hybridization change when polyethylene is prepared from ethylene?

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Write the Lewis structure and molecular formula for each of the following hydrocarbons:

(a) hexane

(b) 3-methylpentane

(c) cis -3-hexene

(d) 4-methyl-1-pentene

(e) 3-hexyne

(f) 4-methyl-2-pentyne

(a) C 6 H 14
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) C 6 H 14
This figure shows five C atoms bonded together with a sixth C atom bonded below the chain. The first C atom (from left to right) has three H atoms bonded to it and is also bonded to another C atom. The second C atom has two H atoms bonded above and below it and is also bonded to another C atom. The third C atom has an H atom bonded above it and a C atom bonded below it. The C atom bonded below the third C atom in the chain has three H atoms bonded to it. The third C atom is also bonded to another C atom. The fourth C atom in the chain has two H atoms bonded above and below it and is bonded to another C atom. The fifth C atom has three H atoms bonded to it. ;
(c) C 6 H 12
This figure shows a C atom with three H atoms bonded to it. This C atom is bonded to another C atom with two H atoms bonded above and below it. The second C atom is also bonded to another C atom down and to the right. This C atom is bonded to one H atom and has a double bond to a fourth C atom. The fourth C atom is also bonded to one H atom. The fourth C atom has a bond up and to the right to another C atom. This C atom has two H atoms bonded above and below it. This C atom also bonds to another C atom which is bonded to three H atoms. ;
(d) C 6 H 12
This figure shows a hydrocarbon chain with a length of five C atoms. The first C atom (from left to right) is bonded to two H atoms and also forms a double bond with the second C atom. The second C atom is bonded to one H atom above it and is also bonded to a third C atom. The third C atom is bonded to two H atoms and also bonded to a fourth C atom. The fourth C atom is bonded to one H atom above it and a C atom below it. The C atom bonded to the fourth C atom in the chain has three H atoms bonded to it. The fourth C atom is also bonded to a fifth C atom which is bonded to three H atoms. ;
(e) C 6 H 10
This figure shows a hydrocarbon chain with a length of six C atoms. The first C atom has three H atoms bonded to it, and it is also bonded to a second C atom. The second C atom has an H atom bonded above and below it. It is also bonded to a third C atom. The third C atom forms a triple bond to a fourth C atom. The fourth C atom forms a single bond with a fifth C atom which has two H atoms bonded above and below it. The sixth C atom has three H atoms bonded to it. ;
(f) C 6 H 10
This figure shows a hydrocarbon chain with a length of five C atoms. The first C atom (from left to right) has three H atoms bonded to it. It is also bonded to a second C atom. The second C atom forms a triple bond to a third C atom. The third C atom forms a single bond with a fourth C atom. The fourth C atom has an H atom bonded above it and a C atom bonded below it. The C atom bonded below the fourth C atom has three H atoms bonded to it. The fourth C atom is bonded to a fifth C atom. The fifth C atom has three H atoms bonded to it.

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Write the chemical formula, condensed formula, and Lewis structure for each of the following hydrocarbons:

(a) heptane

(b) 3-methylhexane

(c) trans -3-heptene

(d) 4-methyl-1-hexene

(e) 2-heptyne

(f) 3,4-dimethyl-1-pentyne

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Give the complete IUPAC name for each of the following compounds:

(a) CH 3 CH 2 CBr 2 CH 3

(b) (CH 3 ) 3 CCl

(c)
This structure shows a hydrocarbon chain composed of C H subscript 3 C H C H subscript 2 C H subscript 3 with a C H subscript 3 group attached beneath the second C atom counting left to right.

(d) CH 3 CH 2 C CH CH 3 CH 2 C CH

(e)
This structure shows a horizontal chain composed of C H subscript 3 C F C H subscript 2 C H subscript 2 C H subscript 2 C H subscript 3 with a C H subscript 2 C H triple bond C H group attached beneath the second C atom counting left to right.

(f)
This structure shows two double bounded C atoms with C l attached to the upper left, C H subscript 3 attached to the lower right, and H atoms attached to the upper right and lower left in the structure.

(g) ( CH 3 ) 2 CHCH 2 CH = CH 2

(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) 5-methyl-1-pentene

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Give the complete IUPAC name for each of the following compounds:

(a) (CH 3 ) 2 CHF

(b) CH 3 CHClCHClCH 3

(c)
This structure shows a hydrocarbon chain composed of C H subscript 3 C H C H subscript 3 with a C H subscript 2 C H subscript 3 group attached beneath the second C atom counting left to right.

(d) CH 3 CH 2 CH = CHCH 3

(e)
This structure shows a hydrocarbon chain composed of C H subscript 3 C H subscript 2 C H subscript 2 C H B r C H subscript 2 C H subscript 3 with a C H subscript 2 C H double bond C H subscript 2 group attached beneath the second C atom counting left to right.

(f) ( CH 3 ) 3 CCH 2 C CH

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Butane is used as a fuel in disposable lighters. Write the Lewis structure for each isomer of butane.

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.
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Write Lewis structures and name the five structural isomers of hexane.

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Write Lewis structures for the cis–trans isomers of CH 3 CH = CHCl.

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.
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Write structures for the three isomers of the aromatic hydrocarbon xylene, C 6 H 4 (CH 3 ) 2 .

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Isooctane is the common name of the isomer of C 8 H 18 used as the standard of 100 for the gasoline octane rating:
The hydrocarbon molecular structure shown includes C H subscript 3 C H C H subscript 2 C C H subscript 3. There is a C H subscript 3 group bonded to the second C atom in the chain (from left to right). There are two C H subscript 3 groups bonded above and below the fourth C atom in the chain.

(a) What is the IUPAC name for the compound?

(b) Name the other isomers that contain a five-carbon chain with three methyl substituents.

(a) 2,2,4-trimethylpentane; (b) 2,2,3-trimethylpentane, 2,3,4-trimethylpentane, and 2,3,3-trimethylpentane:
Three hydrocarbon molecular structures are shown. The first has C H subscript 3 bonded up and to the right to a C atom. The C atom is bonded down and to the right to C H. C H is bonded up and to the right to C H subscript 2. C H subscript 2 is bonded down and to the right to C H subscript 3. The lone C atom is bonded to two C H subscript 3 groups. The C in the C H group is bonded to a C H subscript 3 group. The second structure shows C H subscript 3 bonded up and to the right to C H which is bonded down and to the right to C H. C H is bonded up and to the right to another C H which is bonded down and to the right to C H subscript 3. The initial C atom is bonded to a C H subscript 3 group. The second C atom is bonded to a C H subscript 3 group. The third C atom is bonded to a C H subscript 3 group. The third structure shows C H subscript 3 bonded up and to the right to C H which is bonded down and to the right to C. C is bonded up and to the right to C H subscript 2 which is bonded down and to the right to C H subscript 3. The second C atom is bonded to a C H subscript 3 group. The third C atom is bonded to two C H subscript 3 groups.

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Write Lewis structures and IUPAC names for the alkyne isomers of C 4 H 6 .

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Write Lewis structures and IUPAC names for all isomers of C 4 H 9 Cl.

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.
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Name and write the structures of all isomers of the propyl and butyl alkyl groups.

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Write the structures for all the isomers of the –C 5 H 11 alkyl group.

In the following, the carbon backbone and the appropriate number of hydrogen atoms are shown in condensed form:
Eight structures are shown. The first includes C H subscript 3 bonded to C H subscript 2 bonded to C H subscript 2 bonded to C H subscript 2 bonded to C H subscript 2 with a bond. The second shows C H subscript 3 bonded to C H subscript 2 bonded to C H subscript 2 bonded to C H bonded to C H subscript 3. There is a bond above the fourth C atom (from left to right). The third shows C H subscript 3 bonded to C H subscript 2 bonded to C H bonded to C H subscript 2 bonded to C H subscript 3. There is a bond above the third C atom (from left to right). The five remaining examples involve branching. The fourth structure shows C H subscript 3 bonded to C bonded to C. The second C atom (from left to right) has a bond above it and a bond to an H atom below it. The third C is bonded to two C H subscript 3 groups as well as an H atom. The fifth shows a bond leading to a C H subscript 2 group which is bonded to a C atom. This C atom is bonded to three C H subscript 3 groups. The sixth shows a bond and then C H subscript 2 bonded to C H subscript 2 bonded to C H. The C H is bonded to two C H subscript 3 groups. The seventh shows C H subscript 3 bonded to C H subscript 2 bonded to C with a bond. The C is also bonded to two C H subscript 3 groups. The final structure shows C H subscript 3 bonded to C H subscript 2 bonded to C H. The C H is bonded to a C H subscript 2 group with a bond and a C H subscript 3 group.

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Write Lewis structures and describe the molecular geometry at each carbon atom in the following compounds:

(a) cis -3-hexene

(b) cis -1-chloro-2-bromoethene

(c) 2-pentyne

(d) trans - 6 -ethyl-7-methyl-2-octene

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Benzene is one of the compounds used as an octane enhancer in unleaded gasoline. It is manufactured by the catalytic conversion of acetylene to benzene:
3 C 2 H 2 C 6 H 6

Draw Lewis structures for these compounds, with resonance structures as appropriate, and determine the hybridization of the carbon atoms in each.

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 sp 2 hybridized.

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Teflon is prepared by the polymerization of tetrafluoroethylene. Write the equation that describes the polymerization using Lewis symbols.

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Write two complete, balanced equations for each of the following reactions, one using condensed formulas and one using Lewis structures.

(a) 1 mol of 1-butyne reacts with 2 mol of iodine.

(b) Pentane is burned in air.

(a) CH CCH 2 CH 3 + 2 I 2 CHI 2 CI 2 CH 2 CH 3
A reaction is shown. On the left, a four carbon hydrocarbon chain is shown with a triple bond between C atoms 1 and 2 moving left to right across the molecule. The first C is bonded to one H atom. The second C atom bonds with the third C atom. The third C atom is bonded to two H atoms and a fourth C atom. The fourth C atom is bonded to three H atoms. A plus sign is shown followed by 2 I dash I, which is followed by a reaction arrow, then a four C atom hydrocarbon chain with I atoms bonded above and below C atoms 1 and 2 from left to right. The first C atom is bonded to one H. The third C atom is bonded to two H atoms. The fourth C atom is bonded to three H atoms. ;
(b) CH 3 CH 2 CH 2 CH 2 CH 3 + 8 O 2 5 CO 2 + 6H 2 O
A reaction is shown. On the left, a five C atom hydrocarbon chain is shown with all single bonds between C atoms. Each C atom is bonded to an H atom above and below it. The two C atoms at either end of the chain each have a third H atom bonded to them. A plus sign is shown followed by 8 O double bond O. To the right of the reaction arrow appears 5 followed by O double bond C double bond O plus 6 O bonded to two H atoms.

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Write two complete, balanced equations for each of the following reactions, one using condensed formulas and one using Lewis structures.

(a) 2-butene reacts with chlorine.

(b) benzene burns in air.

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What mass of 2-bromopropane could be prepared from 25.5 g of propene? Assume a 100% yield of product.

65.2 g

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Acetylene is a very weak acid; however, it will react with moist silver(I) oxide and form water and a compound composed of silver and carbon. Addition of a solution of HCl to a 0.2352-g sample of the compound of silver and carbon produced acetylene and 0.2822 g of AgCl.

(a) What is the empirical formula of the compound of silver and carbon?

(b) The production of acetylene on addition of HCl to the compound of silver and carbon suggests that the carbon is present as the acetylide ion, C 2 2− . Write the formula of the compound showing the acetylide ion.

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Ethylene can be produced by the pyrolysis of ethane:
C 2 H 6 C 2 H 4 + H 2

How many kilograms of ethylene is produced by the pyrolysis of 1.000 × 10 3 kg of ethane, assuming a 100.0% yield?

9.328 × 10 2 kg

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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