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Organic Chemistry Flashcards

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1
Q

What is organic chemistry?

A

Organic chemistry is the study of compounds that contain carbon.

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2
Q

What are hydrocarbons?

A

Hydrocarbons are compounds that only contain carbon and hydrogen atoms.

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3
Q

What is an alkane?

A

An alkane is a saturated hydrocarbon.

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4
Q

What is meant by the term ‘saturated’?

A

The term ‘saturated’ refers to a substance in which the atoms are only linked by single bonds (none can be broken to introduce new atoms into the molecule).

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5
Q

State the general formula for alkanes.

A

The general formula for alkanes is CnH2n+2 (where n stands for the number of carbon atoms).

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6
Q

List the first four alkanes.

A

The first four alkanes are methane (CH4), ethane (C2H6), propane (C3H8) and butane (C4H10).

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7
Q

How does the length of a hydrocarbon chain affect its properties?

A

Shorter hydrocarbons are less viscous (more runny), more volatile (lower boiling points) and more flammable (easier to ignite) than longer hydrocarbons.

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8
Q

State the general equation for the complete combustion of a hydrocarbon.

A

The general equation for the complete combustion of a hydrocarbon is:

hydrocarbon + oxygen -> carbon dioxide + water

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9
Q

Describe how crude oil is formed

A

Crude oil is formed from the remains of plants and animals (mainly plankton) that died millions of years ago and were buried in mud. Over millions of years, with high temperature and pressure, those remains turned into crude oil.

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10
Q

What is crude oil used for?

A

The fractions of crude oil are mainly used as fuels or to make other compounds, such as polymers, solvents, lubricants and detergents.

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11
Q

Describe how crude oil is separated into different fractions.

A

Crude oil is separated into fractions (groups of hydrocarbons with similar chain lengths) using fractional distillation. First, the oil is vaporised, and then pumped into a fractionating column with a temperature gradient (it is hot at the bottom and gets cooler as you go up). The longer hydrocarbons, with high boiling points, will condense back into liquids and drain out of the column early on, near the bottom, and the shorter hydrocarbons, with lower boiling points, will condense and drain out much later on, near the top of the column where it is cooler.

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12
Q

What is cracking, and why is it neccessary?

A

Short-chain hydrocarbons are in high demand and low supply, and vice versa. Therefore, we use the process of cracking to turn the longer alkane molecules produced from the fractional distillation of crude oil into shorter, more useful ones.

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13
Q

Describe the two methods of cracking.

A

Cracking is a thermal decomposition reaction (the long chain molecules are broken down by being heated).

One method of doing this is catalytic cracking. To do this, heat long-chain hydrocarbons to vaporise them, and then pass the vapour over a hot powdered aluminium oxide (a zeolite) catalyst. The long-chain molecules will split apart on the surface of the specks of catalyst.

The other method is steam cracking. To do this, vaporise the hydrocarbons, mix them with steam and heat them to a very high temperature.

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14
Q

What are olefins, alkenes and polyenes?

A

According to the IUPAC (International Union of Pure and Applied Chemistry): olefins are unsaturated carbons with one or more double bonds, but no triple bonds (they are alkynes). Alkenes are a type of olefin with only one double bond, and polyenes are a type of olefin with more than one double bond.

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15
Q

What is the general formula for alkenes?

A

The general formula for alkenes is CnH2n (where n is the number of carbon atoms in the chain).

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16
Q

List the first four alkenes.

A

The first four alkenes are ethene (C2H4), propene (C3H6), butene (C4H8) and pentene (C5H10).

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17
Q

Why do alkenes generally not combust completely?

A

In general, there is not enough oxygen in the air for alkenes to combust completely, so they undergo incomplete combustion.

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18
Q

What is the general equation for the incomplete combustion of alkenes?

A

The general equation for the incomplete combustion of alkenes is:

alkene + oxygen -> (any of the following) carbon (soot) + carbon monoxide + carbon dioxide + water

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19
Q

What observation could you make when alkenes burn in air?

A

The incomplete combustion of alkenes results in a smoky yellow flame.

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20
Q

Why are alkenes more reactive than alkanes?

A

Alkanes are saturated, and so very chemically inert, whereas alkenes have a double bond that can open up to leave a single bond and a new atom added to each carbon (these types of reactions are called addition reactions).

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21
Q

How do alkenes react with hydrogen?

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A

Alkenes react with hydrogen in a hydrogenation reaction to form the equivalent alkane. This occurs at a high temperature and with a nickel catalyst.

22
Q

How do alkenes react with steam?

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A

Alkenes react with steam to form alcohols. This occurs at a high temperature with a concentrated acid catalyst.

23
Q

How do alkenes react with halogens?

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A

Alkenes react with halogens to form halogenoalkanes (haloalkanes).

24
How can the addition of bromine water to a double bond be used to test for alkenes?
When orange bromine water is added to a saturated compound, such as an alkane, no reaction will take place and the bromine water will remain orange. However, if bromine water is added to an alkene, the bromine will be added across the double bond, forming a colourless dibromo-compound, and so the bromine water is decolourised.
25
What is a polymer?
A polymer is a chain of repeating monomers.
26
How do you draw the repeating unit and displayed formula of a polymer?
To draw the displayed formula of a polymer, replace the double bond with a single bond and add trailing bonds on either side. To draw the displayed formula, add square brackets and then add the letter 'n' to the right.
27
State the conditions for addition polymerisation.
Addition polymerisation takes place at a high temperature and pressure, with a catalyst and under UV light.
28
What are alcohols?
Alcohols are a homologous series with an -OH functional group.
29
What is a homologous series?
A homologous series is a group of molecules with the same functional group.
30
What is a functional group?
A functional group is a group of atoms within a molecule that determines how that molecule reacts.
31
State the general formula of alcohols.
The general formula of alcohols is CnH2n+1OH (where n is the number of carbon atoms).
32
State the first four alcohols.
The first four alcohols are methanol (CH3OH), ethanol (C2H5OH), propanol (C3H7OH) and butanol (C4H9OH).
33
What similar properties do the first four alcohols share?
The first four alcohols are all flammable (and undergo complete combustion in air), soluble in water (with their solutions having a neutral pH), react with sodium (to form a salt and hydrogen gas) and can all be oxidised to produce a carboxylic acid.
34
What are the main uses of alcohols?
Alcohols can be used to drink (ethanol), as solvents and as fuels.
35
State the conditions at which the fermentation of glucose forms ethanol the quickest.
The fermentation of glucose happens the fastest at a temperature of around 37 °C, in a slightly acidic solution and under anaerobic conditions (no oxygen).
36
What are carboxylic acids?
Carboxylic acids are a homologous series of compounds with the carboxyl (-COOH) functional group.
37
How are carboxylic acids formed?
Alcohols will turn into carboxylic acids in the presence of an oxidising agent (oxygen is a poor oxidising agent, and so ethanol exposed to air will take a while to turn into ethanoic acid).
38
State the first four carboxylic acids.
The first four carboxylic acids are methanoic acid (HCOOH), ethanoic acid (CH3COOH), propanoic acid (C2H5COOH) and butanoic acid (C3H7COOH).
39
State the general formula of carboxylic acids.
The general formula of carboxylic acids is CnH2n+1COOH (where n is the number of carbon atoms, minus 1).
40
What type of acids are carboxylic acids?
Carboxylic acids are weak acids since they only partially dissociate into their ions in solution.
41
How do carboxylic acids react with bases?
Carboxylic acids react with bases to form salts (alongside combinations of water and carbon dioxide). Methanoic acid will form a methanoate, ethanoic acid (vinegar) will form an ethanoate etc.
42
What are esters?
Esters are compounds formed in an esterification reaction between an alcohol and a carboxylic acid. They have the functional group -COO-.
43
How are esters named?
The first part of the name of an ester comes from the alcohol, with 'ol' replaced with 'ly', and the second part comes from the carboxylic acid, with the prefix and 'oate' combined.
44
What is the difference between addition and condensation polymerisation?
Addition polymerisation takes place when identical monomers containing C=C bonds join together, and condensation polymerisation either takes place when two monomer types with two of the same functional groups join together or when one monomer type with two different functional groups join together.
45
State the conditions for an esterification reaction.
Esterification reactions take place at a high temperature and with an acid catalyst.
46
State the name of a compound with two OH functional groups (one at each end).
A compound with two OH functional groups (one at each end) is a diol.
47
State the name of a compound with two COOH functional groups (one at each end).
A compound with two COOH functional groups (one at each end) is called a dicarboxylic acid.
48
What are amino acids?
Amino acids are the building blocks of proteins. They contain two functional groups, an amino group and a carboxyl group. There are 20 different amino acids, from which all the proteins in the body are formed.
49
How are proteins formed?
Proteins are formed in a condensation reaction.
50
How are DNA molecules formed?
DNA molecules are formed from nucleotide polymers.
51
What can glucose molecules form?
Glucose molecules (depending on the isomer) can form starch and cellulose.

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