Chapter 3

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A series of compounds, like the n-alkanes, that differ only by the number of -CH2- groups, is called a(n) (blank) series.

Homologous

Arrange the following conformers of butane in order of energy, lowest to highest: eclipsed, totally eclipsed, gauche, and anti.

anti< gauche< eclipsed<totally eclipsed

If a hydrocarbon has no double or triple bonds, it is said to be ________.

saturated

CH3CH2C(CH3)2CH2CH2I

1-iodo-3,3-dimethylpentane

Place the following alkanes in order of increasing boiling point: CH3(CH2)6CH3, CH3(CH2)5CH3, (CH3)3CCH2CH2CH3

(CH3)3CCH2CH2CH3 <CH3(CH2)5CH3 <CH3(CH2)6CH3

When a mole of decane undergoes complete combustion, how many moles of water are formed?

11

How many methylene groups are present in 2,4-dimethylhexane

2

The structure below is a potent analgesic agent (pain reliever) (J. Med. Chem., 2009, 5685). How many secondary carbons are in this structure?

2

Provide an acceptable name for the [(CH3)3C]2CHCH3.

2,2,3,4,4-pentamethylpentane

Provide the IUPAC name of (CH3)2CHCH2CH2C(CH3)3.

2,2,5-trimethylhexane

[(CH3)2CH]2CHCH3

2,3,4-trimethylpentane

Consider the three isomeric alkanes n-hexane, 2,3-dimethylbutane, and 2-methylpentane.

2,3-dimethylbutane &lt; 2-methylpentane &lt; n-hexane

A bicyclic alkane contains 12 carbon atoms. How many hydrogen atoms does it contain?

22

If an acylic alkane hydrocarbon contains n carbon atoms, how many hydrogen atoms must it also contain?

2n+2

11) How many secondary (2°) carbons are found in 5-ethyl-3,3,4-trimethylheptane?

3

Provide the IUPAC name of (CH3CH2)3CH.

3-ethylpentane

How many methyl groups are present in 2,4-dimethylhexane

4

Provide an acceptable name for (CH3CH2CH2)3CH.

4-propylheptane

Triacontane is an unbranched alkane that contains 30 carbon atoms in each molecule. How many hydrogen atoms are present in each molecule of triacontane?

62

In the complete combustion of heptane, how many moles of water are produced?

8

Which of the following types of hydrocarbons is(are) saturated? A) alkanes B) alkenes C) alkynes D) aromatics E) All of the above are saturated.

A.)alkanes

How many carbons do the primary alkane constituents of gasoline contain?

C) C5=C8

Predict the molecular formula of 4-ethyl-5,5-dimethyldodecane.

C16H34

By using the appropriate molecular formulas, write a balanced equation which describes the complete combustion of cyclohexane.

C6H12 + 9 O2 → 6 CO2 + 6 H2O

By using the appropriate molecular formulas, write a balanced equation which describes the complete combustion of nonane.

CH3(CH2)7CH3 + 14 O2 → 9 CO2 + 10 H2O

Define the term conformation

Conformations are different arrangements of the same molecule formed by rotations about single bonds.

A branched alkane has ________ boiling point relative to the isomeric linear alkane. There are ________ London force interactions in the branched alkane

D) a lower; weaker

Which of the statements below accurately describe(s) alkanes? A) Alkanes are hydrocarbons which contain only single bonds. B) Alkanes belong to the class of unsaturated hydrocarbons. C) Alkanes are the simplest and least reactive class of organic compounds. D) both A and B E) both A and C

E) Both A and C

Which of the following statements concerning the conformers of butane is true?

The gauche and anti conformers differ primarily in the amount of nonbonded strain present.

Which of the following best describes the molecules of a sample of ethane gas at room temperature?

The molecules are rapidly interconverting between the eclipsed and staggered conformations, but at any one time slightly more of them are present in the staggered conformation.

________ is the n-alkane of greatest molecular weight which is a gas at room temperature and pressure.

butane

________ is the reaction process through which long-chain alkanes are converted into a mixture of short-chain alkanes and alkenes.

catalytic cracking

Name the two major steps in the refining of crude oil into usable hydrocarbon products.

fractional distillation cracking(catalytic cracking)

Among the butane conformers, which occur at energy minima on a graph of potential energy versus dihedral angle?

gauche and anti

CH3CH2CH2CH2CH2CH3

hexane n-hexane

A branched alkane generally melts at a ________ temperature than the n-alkane containing the same number of carbons.

lower

Natural gas is primarily composed of

methane

What is the major constituent of natural gas?

methane

Straight-chain alkanes are also called ________.

n-alkanes

List three commercial products which are composed primarily of alkanes.

natural gas,gasolline, kerosene, heating oil, lubricating oil, jet fuel

Which alkanes have largely replaced Freons as propellants in aerosol cans?

propane and butane

When one compares the densities of n-hexane and water, one finds:

that n-hexane is less dense than water

The energy barrier for carbon-carbon bond rotation in propane is mainly due to...

torsion strain

Which intermolecular force is primarily responsible for the interactions among alkane molecules?

van der Waals or London forces


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