Chapter 3
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 < 2-methylpentane < 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
