UNIT 10

CARBON CHEMISTRY

QUÍMICA 1 BATXILLERAT

Isomerism

Two chemical compounds are isomers when they have the same simplified molecular

formula but different developed molecular formulae.

Example:

Planar or structural isomerism (I)

Example:

Planar chain isomerism occurs in

compounds that have the same formula but

that show different ways of arranging

themselves, that is, different chains.

Example:

Planar functional isomerism occurs

in compounds that have the same

formula but different functional

groups.

Planar functional isomerism occurs in compounds that have the same formula

but different functional groups.

Example:

Planar or structural isomerism (II)

Planar positional isomerism occurs in compounds that

have the same formula but that differ in the position of an

atom or a group of atoms, the position of double or triple

bonds or the position of a functional group.

Examples: Position of an atom or group of atoms:

Position of double or triple bonds: Position of a functional group

Spatial isomerism or stereoisomerism (I)

Geometrical spatial isomerism occurs generally in

compounds with a double bond or in cyclic structures in which

the arrangement of atoms, or groups of atoms, around the

same centre is different from one to another.

Examples:cis-2-butene

trans-2-butene

Spatial isomerism or stereoisomerism (II)

Optical spatial isomerism occurs in compounds whose atoms are connected in the

same relative position with respect to a carbon atom, but with a different spatial

arrangement, so that one is the mirror image of the other.

The two compounds are called enantiomers.

Examples:

Polymers

Types of reaction

Condensation polymerisation:

Addition polymerisation:

Macromolecules are formed by the combination of lots of other simple molecules. If these simple molecules are identical structural units that repeat, the macromolecules

are called polymers, and each of the structural units that makes up the polymer is called

a monomer. Polymerisation is the chemical reaction to produce a polymer from a monomer.

Classification of polymers

According to the type of monomer

Homopolymers.

Copolymers.

According to the structure of the polymer

Linear polymers.

Branched polymers.

Natural polymers

Natural

polymers

Cellulose

Proteins

Nucleic acids

Cotton. Linen. Rayon.

Globular polymers. Fibroses.

Deoxyribonucleic acid (DNA). Ribonucleic acid (RNA).

Molecule of cellulose

Molecule of DNA

Synthetic polymers

Resins: condensation polymers in which the monomer has two or more functional

groups (bakelite). Elastomers or synthetic rubbers: addition polymers in which the monomer is a

molecule with double bonds.

Fibres: condensation polymers. Polyamides. Polyesters.

amide bond

Motor fuels: internal combustion

Origin of fuels

Fossil or mineral, from crude oil or

natural gas: petrol, diesel, kerosene,

butane, etc. Derived from modified plant products:

biofuels.

Characteristics of fuels for Otto and diesel motors

Octane number. Heating value. Physical state. Viscosity. Evaluation of pollution: ecological

effects depending on the origin.

Types of combustion engine

Alternating. Alternating internal reaction:

Ignition by spark or Otto motor. Ignition by compression or diesel

motor.

Fuels

Environmental problems caused by the use of coal, oil and natural gas

They are a non-renewable source of

energy and are running out. They generate a large number of

atmospheric contaminants They degrade the areas where oil spillages

occur. They produce carbon dioxide, which is the

main cause of the greenhouse effect.

Biofuels

Biofuels are fuels produced from biomass and, in general, are considered to be

renewable energy.

Types of biofuel Solid: wood, crop residues, animal waste, etc. Liquid: bioalcohol or biodiesel. Gaseous: biogas.

Advantages of the use of biofuels

Biomass is abundant in many regions

of the Earth. It is a renewable resource that does not

produce net emissions of carbon dioxide. It diversifies agricultural activity and

recuperates deforested areas.

Disadvantages of the use of biofuels

The large extent of land needed. Negative effects on the fertility of the

soil, loss of biodiversity and destruction of

the landscape. Problems arising from the use of water

and agrochemical products. Increase in the price of primary

foodstuffs.