Carbon and the Molecular Diversity of Life

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4

EXAMPLE

FUNCTIONAL

PROPERTIES

Carbonyl

Carboxyl

(may be written HO—)

In a hydroxyl group (—OH), a

hydrogen atom is bonded to an

oxygen atom, which in turn is

bonded to the carbon skeleton of

the organic molecule. (Do not

confuse this functional group

with the hydroxide ion, OH–.)

When an oxygen atom is

double-bonded to a carbon

atom that is also bonded to

an —OH group, the entire

assembly of atoms is called

a carboxyl group (—COOH).

Carboxylic acids, or organic

acids

Ketones if the carbonyl group is

within a carbon skeleton

Aldehydes if the carbonyl group

is at the end of the carbon

skeleton

Alcohols (their specific names

usually end in -ol)

Ethanol, the alcohol present in

alcoholic beverages

Acetone, the simplest ketone

Acetic acid, which gives vinegar

its sour taste

Propanal, an aldehyde

Has acidic properties

because the covalent bond

between oxygen and hydrogen

is so polar; for example,

Found in cells in the ionized

form with a charge of 1– and

called a carboxylate ion (here,

specifically, the acetate ion).

Acetic acid

Acetate ion

A ketone and an aldehyde may

be structural isomers with

different properties, as is the

case for acetone and propanal.

These two groups are also

found in sugars, giving rise to

two major groups of sugars:

aldoses (containing an

aldehyde) and ketoses

(containing a ketone).

Is polar as a result of the

electrons spending more time

near the electronegative

oxygen atom.

Can form hydrogen bonds with

water molecules, helping

dissolve organic compounds

such as sugars.

The carbonyl group ( CO)

consists of a carbon atom

joined to an oxygen atom by a

double bond.

Slide 33

Fig. 4-10b

CHEMICAL

GROUP

STRUCTURE

NAME OF

COMPOUND

EXAMPLE

FUNCTIONAL

PROPERTIES

Amino

Sulfhydryl

Phosphate

Methyl

A methyl group consists of a

carbon bonded to three

hydrogen atoms. The methyl

group may be attached to a

carbon or to a different atom.

In a phosphate group, a

phosphorus atom is bonded to

four oxygen atoms; one oxygen

is bonded to the carbon skeleton;

two oxygens carry negative

charges. The phosphate group

(—OPO32–, abbreviated ) is an

ionized form of a phosphoric acid

group (—OPO3H2; note the two

hydrogens).

P

The sulfhydryl group

consists of a sulfur atom

bonded to an atom of

hydrogen; resembles a

hydroxyl group in shape.

(may be

written HS—)

The amino group

(—NH2) consists of a

nitrogen atom bonded

to two hydrogen atoms

and to the carbon skeleton.

Amines

Thiols

Organic phosphates

Methylated compounds

5-Methyl cytidine