Draw the structural formula of
an alkane that has
a) six carbons, all secondary
carbons
b) eight carbons and only pri-
mary hydrogens
c) seven carbons with two isopropyl groups
d)six carbons, three primary and three tertiarycarbons
Answers
Objectives
After completing this section, you should be able to
recognize and name any alkyl group that can be considered to have been formed by the removal of a terminal hydrogen atom from a straight-chain alkane containing ten or fewer carbon atoms.
explain what is meant by a primary, secondary, tertiary or quaternary carbon atom.
represent the various types of organic compounds using the symbol “R” to represent any alkyl group.
Key Terms
Make certain that you can define, and use in context, the key terms below.
alkyl group
methyl group
isopropyl group
sec-butyl group
isobutyl group
tert-butyl group
primary carbon
secondary carbon
tertiary carbon
quaternary carbon
Study Notes
The differences among primary, secondary, tertiary and quaternary carbon atoms are explained in the following discussion. A convenient way of memorizing this classification scheme is to remember that a primary carbon atom is attached directly to only one other carbon atom, a secondary carbon atom is attached directly to two carbon atoms, and so on.
The IUPAC system requires first that we have names for simple unbranched chains, as noted above, and second that we have names for simple alkyl groups that may be attached to the chains. Examples of some common alkyl groups are given in the following table. Note that the "ane" suffix is replaced by "yl" in naming groups. The symbol R is used to designate a generic (unspecified) alkyl group.
Table 3.4.1 : Alkyl Group names
Group
CH3–
C2H5–
CH3CH2CH2–
(CH3)2CH–
CH3CH2CH2CH2–
(CH3)2CHCH2–
CH3CH2CH(CH3)–
(CH3)3C–
R–
Name
Methyl
Ethyl
Propyl
Isopropyl
Butyl
Isobutyl
sec-Butyl
tert-Butyl
Alkyl
Alkyl Groups
Alkanes can be described by the general formula CnH2n+2. An alkyl group is formed by removing one hydrogen from the alkane chain and is described by the formula CnH2n+1. The removal of this hydrogen results in a stem change from -ane to -yl. Take a look at the following examples.
NamingAlkanes-Alkyl.gif
The same concept can be applied to any of the straight chain alkane names provided in Table 3.4.2 .
Table 3.4.2 : straight chain alkane
Methane
CH4
CH4
Ethane
C2H6
CH3CH3
Propane
C3H8
CH3CH2CH3
Butane
C4H10
CH3(CH2)2CH3
Pentane
C5H12
CH3(CH2)3CH3
Hexane
C6H14
CH3(CH2)4CH3
Heptane
C7H16
CH3(CH2)5CH3
Octane
C8H18
CH3(CH2)6CH3
Nonane
C9H20
CH3(CH2)7CH3
Decane
C10H22
CH3(CH2)8CH3
Undecane
C11H24
CH3(CH2)9CH3
Dodecane
C12H26
CH3(CH2)10CH3
Tridecane
C13H28
CH3(CH2)11CH3
Tetradecane
C14H30
CH3(CH2)12CH3
Pentadecane
C15H32
CH3(CH2)13CH3
Hexadecane
C16H34
CH3(CH2)14CH3
Heptadecane
C17H36
CH3(CH2)15CH3
Octadecane
C18H38
CH3(CH2)16CH3
Nonadecane
C19H40
CH3(CH2)17CH3
Eicosane
C20H42
CH3(CH2)18CH3
Answer:
refer to attachment
hope it helps u
