Download Introduction about functional groups

Lecture: 4
Introduction about Functional
Groups
Dr. A.K.M. Shafiqul Islam
27.07.08
Alkanes
Constitutional isomers with the
formula of C5H12.
• Butane and isobutane are constitutional isomers
with the formula of C4H10. The “iso”prefix is two
CH3 attached to a CH.
Constitutional isomers with the
formula of C5H12.
• Pentane, isopentane, and 2,2-dimethylpropane
are constitutional isomers with the formula of
C5H12.
Five constitutional isomers with the
formula of C6H14.
• The constitutional isomers with the formula of
C6H14 are n-hexane, isohexane, 2,2dimethylbutane, 3-methylpentane, and 2,3dimethylbutane.
Nine constitutional isomers with the formula
of C7H16.
• The constitutional isomers with the formula of C7H16 are n-heptane,
2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 2,4dimethylpentane, 2,2-dimethylpentane, 3,3-dimethylpentane, 3ethylpentane, and 2,2,3-trimethylbutane.
Alkyl substituents for the first five
alkyl groups.
• Alkyl substituents for the first five hydrocarbons
are methyl, ethyl, propyl, butyl, and pentyl.
Alkyl substituents for the first five
alkyl groups
• Alkyl substituents for the first five hydrocarbons
are methyl, ethyl, propyl, butyl, and pentyl.
General structures for an alcohol, an
amine, an alkyl halide, and an ether.
• An alcohol is an OH group, an amine is an NH2
group, an alkyl halide has one of the halogens
as a substituent and an ether is an oxygen
placed between two carbons.
Common names of functional
groups
• The alkyl group followed by the name of the
class of the compound yields the common name
of the compound
Ball-and-stick structures of methyl alcohol,
methyl chloride, and methyl amine
• The common names are named with the alkyl group first,
followed by the class of the compound
Primary and secondary carbons
definition
• A primary carbon is attached to one carbon. A
secondary carbon is attached to two carbons
Ball-and-stick structures of
isopropyl chloride
• Two structures may have the same name, but
just look differently
Primary, secondary, and tertiary carbons
• A primary carbon has one other carbon attached
to it. A secondary carbon has two other carbons
attached to it. A tertiary carbon has three other
carbons attached to it
Primary, secondary, and tertiary
hydrogens
• A primary hydrogen is attached to a primary
carbon. A secondary hydrogen is attached to a
secondary carbon. A tertiary hydrogen is
attached to a tertiary carbon
"Sec" prefix in common names
• "Sec" means that the functional group is
attached to the secondary carbon. "Sec" cannot
be used for groups larger than butyl.
"Tert" prefix in common names
• "Tert" means that the functional group is
attached to a tertiary carbon, which is attached
to three other carbons. "Tert" is used for butyl
and pentyl groups only
Names of Some Common Alkyl Groups
• "Iso" is used for two CH3 attached to a CH and the
functional group is attached to the other end. "Sec"
means that the functional group is attached to a
secondary carbon. "Tert" means that the functional
group is attached to a tertiary carbon
Examples of "iso" in common
nomenclature
• If "iso" is used, the compound contains two CH3
on a CH on one end of the structure and the
functional group on the other end of the
structure
Finding the parent chain
• Shown are three different alkanes that both have
8 carbons in the longest parent chain. The
parent chain then becomes octane for all of the
structures.
Numbering of carbon chains
• The longest chain is always numbered such that the
substituents have the lowest possible number. The
substituent and the parent chain are then placed as one
word preceded by the position number of the substituent
Common vs. systematic name
• Only systematic names have numbers; common
names never have numbers.
Numbering the chain in IUPAC
nomenclature
• Number the chain so that the lowest possible
combinations of numbers are used. The groups
are listed in alphabetical order
Multiple identical groups in IUPAC
nomenclature
• When there is more than one of the same
substituent the prefix of di, tri, etc. is used in
front of the substituent's name to indicate their
number. Then each substituent receives a
number in front, separated by a comma
Multiple identical groups in IUPAC
nomenclature
• When there is more than one of the same substituent the
prefix of di, tri, etc. is used in front of the substituent's
name to indicate their number. Then each substituent
receives a number in front, separated by a comma
Numbering the chain in systematic
naming
• Number the chain so that the lowest possible
combinations of numbers are used for the
substituents
If the same substituent numbers are
obtained in both directions, the first group
cited receives the lowest number
• The substituents are listed in alphabetical order
If a compound has two or more chains of the
same length, the parent hydrocarbon is the
chain with the greatest number of
substituents
• The name on the left has two substituents. The
name on the right has one substituent
Names such as "isopropyl," "sec-butyl," and "tertbutyl" are acceptable substituent names in the
IUPAC system of nomenclature, but systematic
substituent names are preferred
• Systematic substituent names are obtained by
numbering the alkyl substituent starting at the
carbon attached to the parent hydrocarbon
Some substituents only have a
systematic name
• Number the longest continuous chain. Number
the substituents so that the lowest possible
combination of numbers are used
Structures of cycloalkanes
• Structures of cyclopropane, cyclobutane,
cyclopentane, and cyclohexane
Skeletal structures of cycloalkanes
• Skeletal structures of the cyclopropane,
cyclobutane, cyclopentane, and cyclohexane
Skeletal structures of alkanes
• Skeletal structures of noncyclic alkanes
In a cycloalkane with an attached alkyl substituent, the
ring is the parent hydrocarbon unless the substituent
has more carbon atoms than the ring. In that case, the
substituent is the parent hydrocarbon and the ring is
named as the substituent
• There is no need to number the position of a
single substituent on the ring
If the ring has two different substituents, they
are cited in alphabetical order and the number
1 position is given to the substituent cited first
• The ring is numbered so that the lowest possible
numbers are used
If there are more than two substituents, the groups are
listed in alphabetical order. The ring is numbered so
that the lowest possible combination of numbers are
used
• All substituents have numbers
Classification of alkyl halides
• A primary halide has a halogen attached to a primary
carbon; a secondary alkyl halide has a halogen
bonded to a secondary carbon; and a tertiary halide
has a halogen attached to a tertiary carbon
Common and systematic names for
alkyl halides
• The common name uses alkyl substituents
followed by the name of the halide. No numbers
are used for common names
Nomenclature of alkyl halides
• The longest continous chain or ring is the parent name.
Number from whichever end that gives the lowest
possible combination of numbers for the substituents
An ether is a compound in which an oxygen
is bonded to two alkyl substituents
• If the alkyl substituents are identical, the ether is
a symmetrical ether. If the substituents are
different, the ether is an unsymmetrical ether
The common name of an ether consists of
the names of the two alkyl substituents,
followed by the word "ether."
• The smallest ethers are almost always named
by their common names
Common nomenclature of
symmetrical ethers
• The prefix "di" is used for naming symmetrical ethers
The IUPAC system names an ether as alkane with
an RO substituent. The substituents are named by
replacing the "yl" ending in the name of the alkyl
substituent with "oxy.“
• The longest R group is the parent compound
Classification of alcohols
• A primary alcohol has an OH attached to a
primary carbon. A secondary alcohol has an OH
attached to a secondary carbon. A tertiary
alcohol has an OH attached to a tertiary carbon
Common nomenclature of alcohols
• Alcohols are named by changing the "ane"
ending on the alkane to "yl" and adding alcohol
Common nomenclature of alcohols
• The common name of an alcohol consists of the
name of the alkyl group to which the OH group is
attached, followed by the word "alcohol."
Systematic names of alcohols
• The systematic name of the alcohol is obtained
by replacing "e" at the end of the name of the
parent hydrocarbon with the suffix "ol." Number
the chain from whichever end that gives the OH
the lowest possible number
IUPAC nomenclature of alcohols
• The position of the functional group is indicated
by a number immediately preceding the name of
the alcohol or immediately preceding the suffix
IUPAC nomenclature of alcohols
• The parent hydrocarbon is the longest continuous chain
containing the functional group. The parent hydrocarbon
is numbered in the direction that gives the functional
group suffix the lowest possible number
If there is a functional group suffix and a
substituent, the functional group suffix gets
the lowest possible number
• Always circle the parent chain first
If counting in either direction gives the same
number for the functional group suffix, the chain is
numbered in the direction that gives a substituent
the lowest possible number
• A number is not needed to designate the position of a
functional group's suffix in a cyclic compound, because it
is assumed to be position 1.
If there is more than one substituent, the
substituents are cited in alphabetical order
• The name of the substituent is named before the
parent hydrocarbon. The functional group is
stated after the parent hydrocarbon.