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INTRODUCTION to FUNCTIONAL
groups
• It is useful to view a molecule as being
composed of two parts. One part only has C’s
that are singly bonded to other C’s (and their
associated H’s)
• This group of atoms is called the alkyl group,
the carbon skeleton, or the carbon framework
and has little effect on the chemical reactions
• The other part of the molecule, where the
action is, is called the functional group. There
is an entire new set of chemical reactions for
each new compound encountered.
• A particular arrangement or group of atoms
has very similar chemistry no matter what the
remainder of the molecule looks like.
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Common functional groups
•
•
•
•
•
•
•
•
Common functional groups
• Carboxylic Acids, RCOOH
• Carboxylic Acid Derivatives:
Alkanes, R-H (and cycloalkanes)
Alkenes, RCH=CHR
Alkynes, R-CΞC-R
Alcohols, R-OH
Aldehydes, RCHO
Alkyl halides, R-X (X=F, Cl, Br,I)
Amines, R-NH2
Aromatics, Ar-H
–
–
–
–
Acid Anhydride, RCOOCOR’
Amide, RCONH2
Acid Chloride, RCOCl
Ester, RCOOR’
• Ether, ROR’
• Ketones, RCOR’
• Nitriles, RCΞN
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Alkanes
• Strictly speaking, alkanes do not have any
functional groups as they form the basic
skeleton on which the functional groups are
attached.
• General formula: CnH2n+2
H H H H
• Examples: H
H H
H C H
H C C H
H
H H
CH4
CH3-CH3
CH4
C2H6
H
C
H
C
C
H
CH3 H
C
Cycloalkanes
• These are alkanes which exist in a ring
• General formula, CnH2n
• Examples
H
H
C
H
CH3 CH2 CH CH2 CH3
CH3
C6H14
CH2
CH2 CH2
CH2 CH2
CH2 CH2
C3H6
C4H8
C2H4
2
CH2 CH2
CH2
C5H10
C6H12
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Alkynes
• The functional group is the triple bond
• General formula: CnH2n-2
• Examples:
The functional group is the double bond
General formula: CnH2n
The simplest alkene has 2 carbon atoms
Examples
double bond
H
H
C C
H
H
CH2
CH2 CH2
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Alkenes
•
•
•
•
CH2
CH2 CH2
CH CH2
triple bond
H3C
H
H
C C
OR H3C CH CH CH3
H3C C C H
H C C H
H3C C C CH2CH2CH3
CH3
C4H8
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Aromatics
Alcohols
• These are a special type of alkenes which have
3 double bonds in a ring.
• The properties are different from normal
alkenes so they are studied differently
• Examples:
H
H
H
C
C
C
C
C
C
•
•
•
•
The functional group is an OH
General formula, R-OH
Alcohols are related to water, H-O-H (H2O)
Examples
H3C O H
H
CH3 CH2 CH2 O H
O H
OR
Phenol (a special
type of alcohol)
H
H
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Aldehydes
Ketones
• The functional group is carbonyl group (C=O)
attached to a hydrogen atom
• General formula, RHC=O
• Examples
• The functional group is carbonyl group (C=O)
attached to an alkyl or an aromatic group
• General formula, R2C=O
Carbonyl group
• Examples
Carbonyl group
O
O
O
H3C C H
H3C C CH3
O
H C H
CH2
H C CH
CH2
OR
O
H
H
O
H3C C CH
OR
CH2 CH2
CH2
O
O
H C
O
CH2 CH2
CH2
O
O
O
H
CH2
CH2
H3C
H
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Amines
Ethers
• The functional group is the amino (NH2)
group
• General formula, RNH2
• Examples
H
N
H
H
H3C N
H
CH3-NH2
• The functional group is the oxygen atom
between two alkyl groups
• The general formula is ROR
• Examples
H3C O CH3
O CH
3
CH3 CH2 CH2 O CH2 CH3
CH3 CH2 CH2 CH2 CH2 NH2
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Alkyl halides
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Carboxylic acid
• The functional group is the halogen atom
• The general formula is RX where X = F, Cl, Br or
I
• Examples
• The functional group is carbonyl acid group
(C=O) attached to a hydroxyl group
• General formula, RCOOH
O
CH
O
O
• Examples
H
C
CH
CH
O
H
2
H3C C O
OR
O
H3C F
CH3 CH2 CH2 Br
H
CH2 CH2
CH2
O
O
Cl
OH
2
H C O
H
H
OH
O
OR
CH3COOH
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HCOOH
COOH
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Amide (a Carboxylic Acid Derivative)
Acid Chloride (a Carboxylic Acid Derivative)
• This compound is derived from carboxylic acid
• General formula, RCONH2
• All carboxylic acid derivatives contain the
carbonyl group (C=O).
• Examples
• This compound is derived from carboxylic acid
• General formula, RCOCl
• Examples
O
H
H3C C N
H
OR
O
H
H C N
H
CH3
O
CH2 C
CH3
CH2 N
H
H
N
NH2
OR
Cl
OR
CH3
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CH3CH2CH2CONHCH3
HCOOH
Acid Anhydride (a Carboxylic Acid Derivative)
This compound is derived from carboxylic acid
General formula, RCOOR’
Sometimes the R and R’ groups are the same
Examples
O
O
OR
CH3
CH2
CH2
C
CH2 O
•
•
•
•
This compound is derived from carboxylic acid
General formula, RCOOCOR’
Sometimes the R and R’ groups are the same
Examples
O
O
O
O
C CH
H3C C O
3
CH3
OR
O
O
O
O
O
CH3
CH2
CH2
C
C
CH2 O
CH2 CH3
O
O
O
O
O
OR
CH3COCH3
CH3CH2CH2COCl
CH3COCl
Ester (a Carboxylic Acid Derivative)
CH3
H3C C O
O
O
H
OR
•
•
•
•
O
CH2
C
CH2 Cl
O
O
CH3COOH
CH3
Cl
O
NH2
O
H3C C Cl
OR
CH3CH2CH2COCH2CH3
CH3COOCOCH3
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CH3CH2CH2COOCOCH2CH3
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Note
Nitriles
• The names of certain functional groups changes when
they are part of a more complex molecule. For
example:
• The functional group is the carbon-nitrogen
triple bond
• The general formula is RCΞN
• Examples
C N
H3C C N
Group
Parent
substituent
OH
Alcohol
hydroxyl
C=O
Ketone/Aldehyde carbonyl
CΞN
Cyanide
nitrile
C=C
Alkene
Double bond
Benzene
Phenyl/ Aryl
CH3 CH2 CH2 C N
• The next slide shows the molecule - Rapamycin
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HO
Hydroxyl
(alcohol)
H3C
Ketone
O
C
Amide
Ketone
O
HO
H3C
C
N
C
C
O
O
O
O
CH3
H
C
C
Hydroxyl
O
C
H3C
OH
H3C O
C
H
H
C
C
C
Frequency of functional groups
H
C
CH3 H
Ether
Double bond
CH3
CH3
Ether
hydroxyl
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O
CH3
Ether
CH3
Frequency
3
Ketone
Double bond
Ether
Amide
3
4
4
1
Ketone
C
H
Group
Hydroxyl (alcohol)
Ketone
Rapamycin
Double bond
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IUPAC nomenclature of organic chemistry
IUPAC nomenclature of organic chemistry
The steps to naming an organic compound are:
• Identify the parent hydrocarbon chain.
• This chain must follow the following rules, in
order of precedence:
– It should have maximum substituents of the suffix
functional group. By suffix, it is meant that the parent
functional group should have a suffix, unlike halogen
substituents. If more than one functional group is
present, use the one with highest precedence.
– It should have maximum number of multiple bonds
– It should have maximum number of double bonds.
– It should have the maximum length.
• Identify the parent functional group, if any,
with the highest order of precedence.
• Identify the side-chains. Side chains are the
carbon chains that are not in the parent chain,
but are branched off from it.
• Identify the remaining functional groups, if
any, and name them by the name of their ions
(such as hydroxy for -OH, oxy for =O ,
oxyalkane for O-R, etc.).
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IUPAC nomenclature of organic chemistry
IUPAC nomenclature of organic chemistry
• Number the chain. To number the chain, first
number in both directions (left to right and right
to left), and then choose the numbering which
follows these rules, in order of precedence:
• Number the various substituents and bonds with
their locants. If there is more than one of the
same type of substituent/double bond, add the
prefix (di-, tri-, etc.) before it. The numbers for
that type of side chain will be grouped in
ascending order and written before the name of
the side-chain. If there are two side-chains with
the same alpha carbon, the number will be
written twice. Example: 2,2,3-trimethyl- .
• If there are both double bonds and triple bonds,
write the "ene" before the "yne".
– Has the lowest locant (or locants) for the suffix
functional group. Locants are the numbers on the
carbons to which the substituent is directly attached.
– Has the lowest locants for multiple bonds (The locant
of a multiple bond is the number of the adjacent
carbon with a lower number).
– Has the lowest locants for double bonds
– Has the lowest locants for prefixes.
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IUPAC nomenclature of organic chemistry
Order of precedence of groups
• In case the main functional group is a terminal
functional group (A group which can only exist at the
end of a chain, like formyl and carboxyl groups), there
is no need to number it.
• Add punctuation: Put commas between numbers (2 5 5
becomes 2,5,5)
• Put a hyphen between a number and a letter (2 5 5
trimethylheptane becomes 2,5,5-trimethylheptane)
• Successive words are merged into one word (trimethyl
heptane becomes trimethylheptane)
Note: IUPAC uses one-word names throughout. This is
why all parts are connected.
• When compounds contain more than one
functional group, the order of precedence
determines which groups are named with
prefix or suffix forms.
• The highest precedence group takes the suffix,
with all others taking the prefix form.
• However, double and triple bonds only take
suffix form (-en and -yn) and are used with
other suffixes.
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Order of precedence of groups
Order of precedence of groups
• Prefixed substituents are ordered alphabetically
(excluding any modifiers such as di-, tri-, etc.),
• If there are multiple functional groups of the
same type, either prefixed or suffixed, the
position numbers are ordered numerically
• The N position indicator for amines and amides
comes before "1", e.g. CH3CH(CH3)CH2CH2NH(CH3)
is N,2-dimethylbutanamine.
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Priority
Functional group
Formula
Prefix
Suffix
1
Carboxylic acids
–COOH
carboxy-
-oic acid*
2
Carboxylic acid derivatives:
Esters
Acyl halides
Amides
–COOR
–COX
–CONH2
R-oxycarbonylhalocarbonylcarbamoyl-
-R-oate
-oyl halide*
-amide*
3
Nitriles
-CN
cyano-
-nitrile*
4
Aldehydes
–CHO
formyl-
-al*
-one
5
Ketones
C=O
Oxo-
6
Alcohol
-OH
hydroxy-
-ol
7
Amines
-NH2
Amino-
-amine
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Alkenes and Alkynes:
Alkene > alkyne
-C=C
-C C-
Chain numbering starts from the end
closest to either group, unless they’re
both equidistant from the chain ends,
in which case the double bond takes
priority and is given the lower
substances containing
double and triple bonds are
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called alkenynes
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