Organic Chemistry

The systematic study of compounds of carbon.

Organic compounds are chemical compounds that occur naturally (can also be synthesised). Carbon’s ability to form a wide range of chemicals and carbon-carbon bonds are strong, and can be made between its self (single, double or triple) or non-metals to form chain like structures or rings.

Hydrocarbons

Simplest organic compounds, but very useful

Made up of only hydrogen and carbon

Saturated hydrocarbons contain only single carbon-carbon bonds

Unsaturated carbons contain double or triple carbon-carbon bonds.

Properties:

·             Generally insoluble in water, and does not react with it

·             More likely to be soluble in non-polar solvents

·             Electro negativities of C and H are very similar, so bond is almost non-polar, symmetry makes molecule non-polar

·             Dispersion forces only, so +size = +boiling point

·             Branching lowers boiling point as they prohibit molecules coming closer

Alkanes

·             Contain only single bonds

·             End in –ane

·             CnH_{2n + 2}

·             Burn in oxygen to form CO₂ and H₂O and energy

·             Substitution reaction with chlorine and fluorine to form haloalkane. Replace hydrogen atoms

Alkenes

·             One double bond between two carbon atoms

·             Ends with –ene

·             CnH_2n

·             Reacts with hydrogen and halogens in addition reaction. Breaks double bond

·             Undergoes self-addition to form polymers

Alkynes

·             One triple bond between two carbon atoms

·             Ends with –yne

·             CnH_{2n -  2}

·             Oxidation/combustion addition reactions

Structural Isomers

·             Organic compounds with the same molecular formula but different structural formulas

·             Different names and chemical properties because molecules have different shapes

Cyclic Hydrocarbons

·             Carbon backbone forms a ring

·             Prefix cyclo-

·             Unsaturated cyclic compounds make up the aromatic series

Naming Organic Substances

1.         Determine longest chain of carbon atoms

2.         Determine if its an -ane -ene or -yne

3.         Determine which end is nearest to a branch, a double bond or a triple bond

: bond/branch

4.         Number the carbon atoms from the end chosen

5.         Name any branches first with the ending –yl  then the longest chain, then any single or double bond

6.         When two or more branches occur on the same carbon atom, the carbon atom is indicated for each branch, with the names given in alphabetical order

7.         When two or more identical branches occur on different carbon atoms, di-, tri- and tetra- are used.

Condensed Formulas

·             Semi-structural formulas

·             Carbon by carbon

·             Brackets are used to indicate side chains, written after the main carbon that they join

·             Or, to represent repeating CH₂ groups

Functional Groups

·             The bond, atom or group of atoms that give a molecule its specific properties

o   Alkenes  C=C

Alcohols (alkanols):

§  Carbon chains containing one or more –OH ‘hydroxy’ groups

§  Ends in –ol

§  Smaller ones, hydrogen bonding is stronger than dispersion forces between same sized alkenes/kanes/kynes \higher boiling point

§  Boiling point increases with size because the non-polar portion of the molecule increases

§  Combustion reaction in air, releasing CO2, water and energy

§  Number of the carbon that –OH is bonded to should be given when naming

Carboxylic Acids:

§  Functional group –COOH ‘carboxy’

§  Add –oic acid to the alkyl prefix

§  Carbon atom is counted when counting how many carbon atoms in chain

§  Weak acids

§  Hydrogen bonding due to –OH gives relatively high boiling point and solubility of smaller molecules

Esters                      

§   

§  low boiling point due to dipole-dipole forces

§  alkyl name first, followed by acid part

Formula	Name	Homologous Series	Naming
-Cl	Chloro	Chloroalkanes	Chloro-
-OH	Hydroxyl	Alkanol	-ol
-O-	Ether	Ether	alkoxyalkane
-NH2	Amino	Alk	-amine
-COOH	Carboxyl	Carboxylic Acid	-oic acid

As alchols get bigger, the polarity affects less of the molecule

Boiling point is higher,

Where Do Hydrocarbons Come From?

·             Crude oil

·             Fractional Distillation separates into its components by using different boiling temperatures

·             Hot crude oil enters the base of the fractioning tower, is vaporised.

o   As the vapours rise, they cool and liquefy at different temps/levels depending on boiling temp.

o   Smallest molecules have lighter fractions, lowest liquid temp, and reach the highest

o   Bubble caps let vapours rise, and allow any condensed liquids to be collected on special trays

Cracking

·             Excess larger hydrocarbons (kerosene) is broken into smaller ones

·             Thermal cracking uses high temps

·             Catalytic cracking uses lower temps and catalysts

·             Important by product are alkenes – raw materials of plastics industry