Functional Groups in Organic Chemistry
Functional Groups
** Carbon
combines with other atoms (e.g., H, N, O, S, halogens) to form structural units
called functional groups.
** Functional
groups are important for three reasons. First, they are the units by which we
divide organic compounds into classes. Second, they are sites of characteristic
chemical reactions. A
particular functional group, in all compounds that contain it, undergoes the
same types of chemical reactions.
** In
addition to the reason up , functional groups serve as a basis for naming
organic compounds. therefore there are a lot of Functional groups.
** Hence, We introduce here several of the
functional groups. We shall have more to say about the structure and properties
of these functional groups in following chapters
(1) Alcohols
** The functional group of an alcohol is an -OH
(hydroxyl) group bonded to a tetrahedral carbon atom (a carbon having single
bonds to four other atoms).
** We can
also represent this alcohol in a more abbreviated form called a condensed structural
formula.
** In a
condensed structural formula, CH3 indicates a carbon bonded to
three hydrogens, CH2 indicates a carbon bonded to two
hydrogens, and CH indicates a carbon bonded to one hydrogen.
** In a
condensed structural formula, we can write alcohol formula without Unshared
pairs of electrons(Oxygen) .
** Thus, the
condensed structural formula for the alcohol with molecular formula C2H6O
is CH3-CH2-OH. It is also common to write these formulas
in an even more condensed manner, by omitting all single bonds: CH3CH2OH.
** Alcohols
are classified as primary (1°), secondary (2°), or tertiary (3°) depending on
the number of carbon atoms bonded to the carbon bearing the -OH group.
Primary alcohols
(1°)
A compound containing a functional group bonded to a carbon atom bonded to only
one other carbon atom and two hydrogens.
Secondary alcohols (2°)
Secondary alcohols (2°)
A compound
containing a functional group bonded to a carbon atom bonded to two other
carbon atoms and one hydrogen atom.
Tertiary alcohols (3°)
Tertiary alcohols (3°)
A compound containing a functional group bonded to a carbon atom bonded to
three other carbon atoms.
(2) Amines
** The functional group of an amine is an amino group, a nitrogen atom
bonded to one, two, or three carbon atom(s) by single bonds.
** Notice that this classification scheme is different from that used with alcohols and halides.
Amino
group
A compound
containing a nitrogen atom bonded to one, two, or three carbon atom(s) by
single bonds.
Primary
(1o) amine
An amine in
which nitrogen is bonded to one carbon and two hydrogens.
Secondary
(2o) amine:
An amine in
which nitrogen is bonded to two carbons and one hydrogen.
Tertiary
(3o) amine:
(3) Aldehydes and Ketones
** The functional group of both aldehydes and ketones is the C=O (carbonyl) group.
** formaldehyde,
CH2O, is the simplest aldehyde, the carbonyl carbon is bonded to two
hydrogens. In all other aldehydes, it is bonded to one hydrogen and one carbon.
** In a
condensed structural formula, the aldehyde group may be written showing the
carbon oxygen double bond as -CH=O; alternatively, it may be written -CHO.
** In a
ketone, the carbonyl carbon is bonded to two carbon atoms.
Carbonyl group
A C = O group.
Aldehyde
A compound
containing a -CHO group.
Ketone
(4) Carboxylic Acids
** The functional group of a carboxylic acid is a -COOH (carboxyl: carbonyl+ hydroxyl) group.** In a condensed structural formula, we can write a carboxyl group like this -CO2H.
Carboxylic acid:
A
compound containing a carboxyl, -COOH, group.
Carboxyl
group:
A
-COOH group.
** As the model shows, the group is planar, something we will explain later.
(5) Esters
A carboxylic ester, commonly referred to as an
ester, is a derivative of a carboxylic acid in which the hydrogen of the
carboxyl group is replaced by a carbon- containing group.
Carboxylic
ester:
A
derivative of a carboxylic acid in which H of the carboxyl group is replaced by
a carbon.
(6) Amides
** The last functional group we will explain here is A carboxylic amide, it is commonly referred to as an amide, is a derivative of a carboxylic acid in which the -OH of the carboxyl group is replaced by an amine.** As the model shows, the group is planar, something we will explain later.
Amide:
A
derivative of a carboxylic acid in which the -OH is replaced by an amine.
(7) Common Functional groups used in Organic Chemistry
In conclusion, the table blow indicates most of all Functional groups used in Organic Chemistry:
Reference: Organic
chemistry / William H. Brown , Christopher S. Foote , Brent L. Iverson ,
Eric V. Anslyn , Bruce M. Novak . ( sixth edition) . United States
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