Carbon and Organic Compounds

The position of carbon in the periodic table.

Carbon’s Key Properties

• Has a mid-range electronegativity value so it forms covalent bonds and shares electrons

• Can form a maximum of four bonds• Can form chains, sheets, and rings• Usually combined with H and often bonds

with O, S, N and P

Forms

HYDROCARBONS

Carbon Skeletons and Hydrogen Skins

Each C can form a maximum of four single bonds, OR two single and one double bond, OR one single and triple bond.

The arrangement of C atoms determines the skeleton, so a straight chain and a bent chain represent the same skeleton.

Groups joined by single bonds can rotate, so a branch pointing down is the same as one pointing up.

The Other Carbon Bonds

• If carbon is not bound to anything else in an organic compound, it will be attached to hydrogen.

C – C – C – C – C|C

Ways of depicting formulas and models of an alkane.

Some five-carbon skeletons.

CC C C C

CC C C

C

CC C

C

C

C C C CC

CC C C C

CC C C

C

CC C C

C

CC C

C C

C

C C

CC

C C

C

C C

C

C

C

C C

C C

C

C C

CC C C

C

single bonds double bond

ring

Saturated and Unsaturated

• When the carbon in organic compounds forms only single bonds we say that the compound is saturated (can’t add anything more).

• If there are double or triple bonds, these can be broken to add more atoms. In this case we say that the compound is unsaturated.

Isomers

• When two compounds have the same chemical formula but different structural formulas they are called isomers.

• There are many kinds of isomers depending on where the carbons are placed and how bonds are arranged.

Isomers and Vision• If you take beta carotene and split the

molecule, you get 2 Vitamin A molecules. These are related to retinal.

• Retinal changes form when a photon of light strikes it.

• http://www.elmhurst.edu/~chm/vchembook/531vision.html

Depicting cycloalkanes.

C

C C

H H

H

HH

H

C

C C

CH

H

H

H

H

H H

H

cyclopropane

cyclobutane

Boiling points of the first 10 unbranched alkanes.

An analogy for optical isomers.

Some molecules with the alcohol functional group.

Some common aldehydes and ketones.

methanal (formaldehyde) used to make

resins in plywood, dishware,

countertops; biological

preservative

ethanal (acetaldehyde)

narcotic product of ethanol

metabolism; used to make perfume, flavors, plastics, other chemicals

benzaldehyde artificial almond

flavoring

2-propanone (acetone) solvent for fat, rubber, plastic, varnish, lacquer;

chemical feedstock

2-butanone (methyl ethyl

ketone) important solvent

Some molecules with the carboxylic acid functional group.

methanoic acid (formic acid) an irritating

component of ant and bee stings

butanoic acid (butyric acid)

odor of rancid butter; suspected component

of monkey sex attractant

octadecanoic acid (stearic acid)

found in animal fats; used in making candles

and soap

benzoic acid calorimetric

standard; used in preserving food,

dyeing fabric, curing tobacco

Some lipid molecules with the ester functional group.

cetyl palmitate the most common

lipid in whale blubber

lecithinphospholipid found in all cell membranes

tristearin typical dietary fat used as an

energy store in animals

Polymers

• Long chain molecules made of small repeating units

• Can be made by addition reactions (adding molecules) or condensation (splitting something out and joining the pieces.

• Building polymers….

Crosslinking

• Some polymers make bridges across chains rather than just adding to chains. These are “cross-linked” polymers.

• Some cross-links are covalent bonds and are permanent. Some links are made with intermolecular forces and can be broken more easily (like the alginate worms).