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IGCSE Chemistry > Organic Chemistry - Compounds > Flashcards

Organic Chemistry - Compounds Flashcards

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1
Q

What are the four important families of organic compounds?

A
  • the alkanes
  • the alkenes
  • the alcohols
  • the carboxylic acids
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2
Q

If the name of an organic compound ends in -ane, which family does it belong to?

A

the alkanes

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3
Q

If the name of an organic compound ends in -ene, which family does it belong to?

A

the alkenes

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4
Q

If the name of an organic compound ends in -ol, which family does it belong to?

A

the alcohols

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5
Q

If the name of an organic compound ends in -oic acid, which family does it belong to?

A

the carboxylic acids

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6
Q

If the name of an organic compound starts with meth-, how many carbon atoms does it have?

A

one

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7
Q

If the name of an organic compound starts with eth-, how many carbon atoms does it have?

A

two

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8
Q

If the name of an organic compound starts with prop-, how many carbon atoms does it have?

A

three

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9
Q

If the name of an organic compound starts with but-, how many carbon atoms does it have?

A

four

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10
Q

If the name of an organic compound starts with pent-, how many carbon atoms does it have?

A

five

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11
Q

If the name of an organic compound starts with hex-, how many carbon atoms does it have?

A

six

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12
Q

What is a functional group?

A

A functional group is the part of a molecule that largely dictates how the molecule will react.

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13
Q

What is a homologous series?

A

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.

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14
Q

What are isomers?

A

Isomers are compounds with the same formula, but different structures.

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15
Q

What differences in physical properties are there between linear isomers and branched isomers?

A

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.

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16
Q

What are some key points about the alkanes?

A
  • 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
17
Q

Describe the reaction between alkanes and chlorine.

A

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.

18
Q

What are some key points about the alkenes?

A
  • 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.
19
Q

What is cracking?

A

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:

  1. The long-chain hydrocarbon is heated to vaporise it
  2. The vapour is passed over a hot catalyst
  3. Thermal decomposition takes place

Cracking produces more reactive compounds that can have more uses than the original long-chain hydrocarbon.

20
Q

What is an addition reaction?

A

An addition reaction is one that turns an an unsaturated alkene into a saturated compound.

21
Q

What is polymerisation?

A

This is an addition reaction where alkene molecules add on to each other to form long-chain compounds called polymers.

22
Q

How can you test whether a hydrocarbon is saturated or unsaturated?

A

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.

23
Q

What are some key points about the alcohols?

A
  • not hydrocarbons
  • form a homologous series with the general formula C<em>n</em>H2n+1OH
  • have the OH functional group
24
Q

How can ethanol be made?

A
  • Fermentation
  • Hydration of ethene
25
Q

What are the uses of ethanol?

A
  • 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
26
Q

What are some key points about the carboxylic acids?

A
  • 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
27
Q

How is ethanoic acid formed?

A
  • oxidation of ethanol by fermentation
  • oxidation of ethanol with acidified potassium mangante(VII)
28
Q

What are some reactions of ethanoic acid that show it is a typical weak acid?

A
  • 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
29
Q

How are esters formed?

A

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

IGCSE Chemistry (15 decks)

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