Organic Chemistry - Compounds Flashcards
What are the four important families of organic compounds?
- the alkanes
- the alkenes
- the alcohols
- the carboxylic acids
If the name of an organic compound ends in -ane, which family does it belong to?
the alkanes
If the name of an organic compound ends in -ene, which family does it belong to?
the alkenes
If the name of an organic compound ends in -ol, which family does it belong to?
the alcohols
If the name of an organic compound ends in -oic acid, which family does it belong to?
the carboxylic acids
If the name of an organic compound starts with meth-, how many carbon atoms does it have?
one
If the name of an organic compound starts with eth-, how many carbon atoms does it have?
two
If the name of an organic compound starts with prop-, how many carbon atoms does it have?
three
If the name of an organic compound starts with but-, how many carbon atoms does it have?
four
If the name of an organic compound starts with pent-, how many carbon atoms does it have?
five
If the name of an organic compound starts with hex-, how many carbon atoms does it have?
six
What is a functional group?
A functional group is the part of a molecule that largely dictates how the molecule will react.
What is a homologous series?
A homologous series is a group of similar compounds that share similar properties due to the presence of the same functional group, and share the same general formula.
As the chain length increases (by 1 each time), m.p. and b.p. increase, viscosity increases and flammability decreases.
What are isomers?
Isomers are compounds with the same formula, but different structures.
What differences in physical properties are there between linear isomers and branched isomers?
Branched isomers have lower melting/boling points, as the branches make it harder for the molecules to be close to each other, so the intermolecular forces are weaker.
What are some key points about the alkanes?
- Simplest family of organic compounds
- Hydrocarbons
- Form a homologous series with the general formula C<em>n</em>H2n+2
- C–C bonds are all single bonds, so they are saturated
- Found in petroleum and natural gas
- 1st four are gases, next 12 are liquids, rest are solids (at r.t.p.)
- Generally unreactive, but burn well in good O2 supply, so are used as fuels
- React with chlorine in sunlight
Describe the reaction between alkanes and chlorine.
A substitution reaction can take place bewteen alkanes and chlorine, where a chlorine atom takes the place of a hydrogen atom. If there is enough chlorine, all the hydrogen atoms will be replaced. This reaction can be explosive, but only in sunlight as it is a photochemical reaction: light energy is needed to break the bonds in the chlorine molecules.
What are some key points about the alkenes?
- Hydrocarbons
- Form a homologous series, with the general formula C<em>n</em>H<em>2n</em>
- Contain the C = C double bond that is their functional group, and so are called unsaturated.
- Made from alkanes by cracking (this also produces hydrogen)
- Much more reactive than alkanes
- Undergo addition reactions.
What is cracking?
This is a reaction in which long-chain hydrocarbon molecules are broken down to shorter, more useful molecules containing the C=C double bond using the following steps:
- The long-chain hydrocarbon is heated to vaporise it
- The vapour is passed over a hot catalyst
- Thermal decomposition takes place
Cracking produces more reactive compounds that can have more uses than the original long-chain hydrocarbon.
What is an addition reaction?
An addition reaction is one that turns an an unsaturated alkene into a saturated compound.
What is polymerisation?
This is an addition reaction where alkene molecules add on to each other to form long-chain compounds called polymers.
How can you test whether a hydrocarbon is saturated or unsaturated?
Add the hydrocarbon to an aqueous solution of bromine (which is orange in colour). If a C=C bond is present, an addition reaction takes places and the colour disappears.
What are some key points about the alcohols?
- not hydrocarbons
- form a homologous series with the general formula C<em>n</em>H2n+1OH
- have the OH functional group
How can ethanol be made?
- Fermentation
- Hydration of ethene
What are the uses of ethanol?
- Alcohol in alcoholic drinks
- Solvent - dissolves many substances that do not dissolve in water; is volatile (suitable for perfume)
- Fuel - burns well in oxygen; can be made cheaply from waste plant material; less impact on CO2 levels
What are some key points about the carboxylic acids?
- not hydrocarbons
- forms a homologous series with the general formula C<em>n</em>H<em>2n</em>O2
- has the functional group COOH, also known as the carboxyl group
How is ethanoic acid formed?
- oxidation of ethanol by fermentation
- oxidation of ethanol with acidified potassium mangante(VII)
What are some reactions of ethanoic acid that show it is a typical weak acid?
- solution turns litmus red
- solution contains H+ ions
- since only some molecules dissociate in water, ethanoic acid is a weak acid
- reacts with metals, bases, and carbonates to form ionic salts
How are esters formed?
Esters are compounds formed from the reaction of ethanoic acid with alcohols.
- two molecules join to make a larger molecule with the loss of water, so this is a condensation reaction
- the reaction is reversible
- the alcohol part comes first in the name but second in the formula, e.g. propyl ethanoate is CH3COOC3H7
- esters often have attractive smells
