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.