C6.2 Organic Chemistry Flashcards
What are hydrocarbons:
= compounds that contain only hydrogen atoms & carbon atoms
Name hydrocarbons:
- alkanes
- alkenes
Derivative hydrocarbons:
- alcohols
- carboxylic acids
Homologous series:
a family of hydrocarbons with similar chemical properties who share the same general formula
Why do alkenes, alkanes, alcohols & carboxylic acids all form their own homologous series?
- same general formula
- each successive member differs by a CH2 group (ALL)
- same functional group (NOT ALKANES)
- similar chemical reactions
Why are all alkanes saturated?
= carbon atoms joined together by single covalent bonds, no atoms can be added
(C-C bonds)
(Part of alkanes homologous series)
General formula of alkanes:
= C H
n 2n+2
Names of alkanes in order:
Methane Ethane Propane Butane Pentane Hexane Heptane Octane
How do alkanes react
= combustion, react with oxygen in air & burn
What molecules undergo combustion (complete/incomplete)?
- alkenes
- alkanes
- alcohols
Complete combustion:
If there is a plentiful supply of oxygen/air
- carbon atoms oxidised to carbon dioxide
- hydrogen atoms oxidised to water
(Products = CO2 & H2O)
Incomplete combustion
If there is a poor supply of oxygen/air
- hydrogen atoms oxidised to water
- carbon atoms oxidised to carbon monoxide, or not oxidised at all
(Products = CO, C, H2O)
Why is incomplete combustion not good?
= carbon monoxide (CO) is formed
- it’s a toxic gas & can cause suffocation
General formula of alkenes:
= C H
n 2n
Why are alkenes unsaturated?
= contain carbon-carbon double covalent bond, more atoms can be added
(C=C bond)
(part of alkene homologous series)
Name of alkenes in order:
Ethene Propene Butene Pentene Hexene
(NO METHENE)
Why does methene not exist?
Because the formula would be CH2, and there can’t be 1 carbon because it has to contain a carbon-carbon double bond so alkenes must contain at least 2 carbons
How do alkenes react? (1)
- = combustion, burn in oxygen/air (incomplete/complete)
What allows alkenes to take part in a wider range of reactions?
= alkenes have a functional group = carbon-carbon double bond
It lets alkenes undergo addition reactions
What is a functional group?
= an atom, group of atoms, or type of bond in a molecule that determines the chemical reactions of an organic compound
What do alkenes react with in addition reactions?
- bromine, to form colourless ‘dibromo’ compounds
- hydrogen, in the presence of a nickel catalyst, to form alkanes
What are addition reactions?
= an atom or group of atoms combines with a molecule to form a larger molecule, with no other product
Example of an addition reaction between an alkene and bromine:
Ethene + Bromine —> Dibromoethane
C2H4 + Br2 —> C2H4Br2
(C=C bond in ethene, C-C bond in dibromoethane)
Example of an addition reaction with an alkene & hydrogen:
Ethene + Hydrogen —> Ethane
C2H4 + H2 —> C2H6
How can we test if a substance is an alkane or alkene?
= test for unsaturation: bromine react with alkenes but no alkanes
- bromine water is orange-brown, turns colourless when mixed with alkenes, remains same with alkanes
general formula of alcohols:
C H OH
n 2n+1
Name alcohols in order:
Methanol Ethanol Propanol Butanol Pentanol Hexanol
What is the functional group for alcohols?
What extra reactions does it allow alcohols to undergo?
= hydroxyl group, -OH
= can be oxidised to form carboxylic acids
(usually only the hydroxyl group take part in the reactions, not other atoms in alcohol)
General formula of carboxylic acids:
C H COOH
n(-1) 2n+1
(-1 from first carbon atom as carbon atom in carboxyl group, eg. Pentane = C4H9COOH)
Functional group of carboxylic acids:
= carboxyl group, -COOH
name carboxylic acids in order:
= -anoic acid Methanoic acid Ethanoic acid Propanoic acid Butanoic acid Hexanoic acid