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Chemistry > Ch.15 - Organic Compounds > Flashcards

Ch.15 - Organic Compounds Flashcards

1
Q

What are saturated and unsaturated organic compounds?

A

Saturated chemical compounds only contain single bonds. In saturated organic compounds, all carbon atoms are tetrahedral.

Unsaturated chemical compounds contain a double or triple bond.

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2
Q

What are aromatic and aliphatic compounds?

A

Aromatic compounds contain a benzene ring. Aliphatic compounds don’t have a benzene ring.

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3
Q

What are alkanes? Give the general formula for alkanes.

A

Alkanes form a homologous series of aliphatic hydrocarbons. They are saturated compounds. They are non-polar. CnH2n+2

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4
Q

What are alkenes? Give their general formula. What causes their increasing boiling point?

A

Alkenes form a homologous series of aliphatic hydrocarbons. They are unsaturated compounds, containing a non-polar carbon=carbon double bond. CnH2n. Van der Waals’ forces increases the boiling point of hydrocarbons as the number of carbons increases. They are either non-polar or slightly polar. Low solubility in water, high solubility in non-polar substances.

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5
Q

What are hydrocarbons?

A

Hydrocarbons are compounds of carbon and hydrogen only which are covalently bonded.

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6
Q

What is a planar carbon compound?

A

A planar carbon compounds have a C=C or C=O double bonds.

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7
Q

What are mercaptans?

A

Mercaptans are added to natural gases. They have a strong smell (usually of S) to alert for leaks.

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8
Q

What are structural isomers?

A

Structural isomers are compounds that have the same molecular formula but different structural formulae.

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9
Q

What causes alkanes increasing boiling points? Name the states of the alkanes.

A

Alkanes with longer C chains have stronger van Der Waals’ forces between molecules. The attraction requires more energy to break apart. Methane to butane are gases. Pentane and above are liquids at room temperature. More than 15 carbons gives a waxy liquid alkane.

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10
Q

Name non-polar substances.

A

Cyclohexane and methylbenzene.

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11
Q

What are alkynes?

A

Alkynes form a homologous series of aliphatic hydrocarbons. CnH2n-2. Suffix: -yne
Each alkyne contains a carbon triple bond. Alkynes are unsaturated. They are non-polar. Lower alkynes are gases while higher alkynes are liquids or solids at room temperature. Methyne is non-existant.

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12
Q

What is auto-ignition?

A

Auto-ignition is ignition in an internal combustion engine before a spark is produced by the spark plug.

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13
Q

What is an octane number?

A

An octane number is a measure of the tendency of a fuel to resist auto-ignition.

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14
Q

What is the fractional distillation of crude oil(fractionation)?

A

Fractional distillation is the separation of crude oil, using distillation, into components according to their boiling points.

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15
Q

Draw the diagram for fractional distillation.

A
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16
Q

How does auto-ignition(knocking) occur?

A

Auto-ignition occurs when the reaction between petrol and air happens too soon due to increased pressure in the engine and low octane fuels. The petrol and oxygen should explode as a result of the spark plug.

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17
Q

What influences the octane number of hydrocarbons?

A

In straight-chained hydrocarbons, the shorter the alkane, the higher the octane number(isomerisation). In branched-chained hydrocarbons, the greater the number of branches, the higher the octane number. Cyclic and aromatic hydrocarbons have a higher octane number(dehydrocyclisation). The addition of oxygenates.

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18
Q

What is the octane number of 2,2,4-trimethylpentane and heptane.

A

2,2,4-trimethylpentane has an octane number of 100, while heptane has one of 0.

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19
Q

What is catalytic cracking?

A

Catalytic cracking is the splitting of long-chain hydrocarbons into smaller molecules using heat and catalysts.

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20
Q

What are the advantages of catalytic cracking?

A

Long-chain compounds are converted into more useful compounds. Branched chain alkanes with shorter chain lengths are formed that have high octane numbers and are used for making petrol. Alkenes are formed, which are the starting compounds for the manufacture of polymers.

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21
Q

What is hydrogen used for?

A

Hydrogen is used for manufacturing ammonia, hydrogenation of vegetable oils to make margarine and manufacturing HCl.

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22
Q

How is hydrogen produced on a large scale?

A

Hydrogen may be produced on a large scale by steam reforming of natural gas or by electrolysis of water.

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23
Q

What is refinery gas?

A

Refinery gas is the fraction with the lowest boiling point. It is sold for domestic use. Propane and butane can be liquified from this fraction under pressure, it is called LPG(liquid petroleum gas).

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24
Q

What is light gasoline and naptha?

A

Light gasoline is used to make petrol. Naphtha is used to make raw material for the petrochemical industry.

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25
Q

What is the use of kerosene?

A

Kerosene(paraffin oil) is used as a domestic heating oil and as jet fuel.

26
Q

What is gas oil?

A

Gas oil is used as diesel for engines. Also used in domestic heating(cleaner than kerosene).

27
Q

What is the use of fuel oil and residue?

A

Fuel oil is used in ships and power stations. Residue is used to make lubricating oils and bitumen for roads.

28
Q

What additives to petrol increase its octane number?

A

Lead compounds and oxygenates.

29
Q

Why is lead not added to petrol?

A

Leaded petrol harms the environment by producing toxic fumes and also acts as a catalyst poison on catalytic converters.

30
Q

What are sources of hydrogen?

A

Electrolysis of water, dehydrocyclisation and steam reforming.

31
Q

How is crude oil factionally distilled?

A

Crude oil is continuously added to a furnace, where it is evaporated. The vapour passes up the fractionating tower. Fractions condense at different levels depending on their boiling point. Higher boiling points being at the bottom and lower boiling points on the top.

32
Q

What is a chloroalkane?

A

A chloroalkane is an alkane in which one or more of the hydrogen atoms are replaced with chlorine atoms. Chloroalkanes are used in dry-cleaning products. Some are harmful to the environment.

33
Q

What is an alcohol?

A

Alcohols form a homologous series of organic compounds, containing a hydroxyl group. CnH2n+1OH. They are formed when a hydroxyl group replaces a hydrogen in alkanes. They are tetrahedral.

34
Q

Why do alcohols have a higher boiling point than alkanes?

A

The presence of the polar OH group in alcohols results in hydrogen bonding in alcohol molecules.

35
Q

What are ketones?

A

Ketones form a homologous series of compounds, with general formula R1COR2, where R1 and 2 are alkyl groups.

36
Q

What are alkyl groups?

A

CnH2n+1

37
Q

What are carboxyl groups?

A

R-COOH, where R is the organic compound and C is connected with O with a double bond.

38
Q

What is a carbonyl group?

A

A carbonyl group is C=O (double bond).

39
Q

Mandatory experiment:
Preparation of ethyne.
-Give formula and diagram
-What type of reaction is involved?
-Give method
-Describe appearance of CaC2
-Why is copper sulphate solution used?
-Why is the first tube discarded?(SH)

A

Set up apparatus like diagram. Place water into the flask dropwise. Collect the gas in test tubes and stopper each gas-filled tube underwater.
This addition reaction is exothermic.
CaC2 is a grey solid.
The copper sulphate solution removes impurities such as hydrogen sulphide and phosphine.
The 1st tube is discarded as it could form an explosive mixture.

40
Q

What are ethene and ethyne’s properties and how are they proven? What is the difference between the flame test for ethyne and ethene?

A

C2H2 is an unsaturated compound and it is non-polar. This is proven because it turns Br2 water from orange to colourless. It turns KMnO4 solutions from purple to colourless. When a test tube of the gas is ignited, a luminous flame is produced. C2H4 produces a little soot. C2H2 produces a lot of soot. Adding limewater to the test tube turns it milky. This shows that CO2 is formed when ethyne reacts with air.

41
Q

Mandatory experiment:
Preparation of ethene
-Give formula, with the structural formulae and diagram
-What type of reaction is involved?
-Give method
-Describe appearance of Al2O3
-Give one measure of safety
-Why is the first tube discarded?(SH)

A

This is an elimination reaction. It is an example of heterogeneous catalysis.
Ethanol is put in first, then glass wool to soak it up. The boiling tube is placed horizontally. The Al2O3 is heated.
Al2O3 is a white powder.
Avoid ‘suck-back’ by removing cork before the flame is turned off after the experiment. H2O not Ca(OH)2 in formula.

42
Q

What are the uses of ethene?

A

Ethene is used to make polythene and ethanol.

43
Q

What are the uses of ethyne?

A

Ethyne is used in welding to produce a hot flame that can cut metal. Ethyne burns with a spark free flame so it is used in miners’ lamps.

44
Q

Mandatory experiment:
Recrystallisation of benzoic acid
-method

A

Dissolve impure benzoic acid in a minimum quantity of hot solvent. Filter using a Buchner system to remove any insoluble impurities. Cool to recrystallize. Filter to retrieve crystals. Wash crystals with cold solvent. Dry in dessiccator.

45
Q

Mandatory experiment:
Melting point determination of benzoic acid.
-method
-diagram

A

Take a small sample of benzoic acid. Heat on aluminium block with thermometer in it. Note the temperature the samples melt at.
The pure sample melts at a sharp temperature while the impure sample melts over a wide range of temperatures. The impure sample melts at a lower temperature than the pure sample.

46
Q

Mandatory experiment:
The extraction of eugenol from clove by steam distillation.
-method
-diagram
-safety precautions

A

Place the cloves in a pear shaped flask. Place water in the steam generator, connect and boil. Use anti-bumping granules in the steam generator. After 30 minutes, disconnect the steam generator to avoid suckback, then turn off the heat. Collect 50cm^3 of pale milky distillate(emulsion). Note smell.

Have a safety opening on the boiling flask to prevent a build-up of pressure. If the level of water is too low, the system will not work well. Remove heat, carefully loosen safety valve and top-up the flask with water. Reconnect everything and heat again.

47
Q

What principle is steam distillation based on?

A

Steam distillation is a method that uses the principle that when 2 immiscible liquids are together, their boiling point is lower than either of the 2 pure compounds alone.

48
Q

What are the uses of clove oil?

A

Clove oil can be used as a flavouring and as a preservative. Its is an antiseptic. It is also a treatment for toothache.

49
Q

Why is steam distillation used for eugenol extraction?

A

Steam distillation is used as some components of clove oil have a high boiling point and the required temperature for simple distillation would partially decompose molecules in the oil.

50
Q

Mandatory experiment:
Solvent extraction of eugenol
-method
-diagram
-safety precautions

A

Place oil and cyclohexane in a separating funnel. Shake the contents of the funnel. Collect the organic solvent fraction. Let the lower aqueous layer run off. The distillate is washed out 3 times using 10cm^3 of cyclohexane each time to increase the amount of eugenol extracted. The organic layer was run into a beaker. Leave overnight for cyclohexane to evaporate, leaving the clove oil behind.

Release pressure carefully by opening the separating funnel when upside down.

51
Q

Describe the bonding in benzene.

A

Benzene contains 6 C atoms joined to form a hexagonal planar ring. Each C has 4 valence electrons. Of these 1 is used to form a sigma bond with a H atom. 2 other electrons are used to form sigma bonds with the C atoms on either side. The remaining 1 electron not involved in sigma bonding is shared between the 6 C atoms, bonds the H and C atoms. The ring in the centre contains a delocalised pi bond.

52
Q

What are aldehydes?

A

Aldehydes form a homologous series of compounds with a general formula of CnH2n+1CHO. They have the suffix -al.

53
Q

What are carboxylic acids?

A

Carboxylic acids form a homologous series of compounds with the general formula CnH2n+1COOH. Where methanoic acid is when n=0.

54
Q

Explain the acidic nature of the carboxylic acid functional group.

A

The carboxylic acid functional group (RCOOH) donates a proton creating the carboxylate ion. This leaves a stable arrangement with a delocalised charge.

55
Q

What are esters?

A

Esters are compounds derived from carboxylic acids with the formula R1COOR2. The ester linkage -COO- contains a planar carbon.

56
Q

What are the properties of esters?

A

Short chain esters are liquids at room temperature. The C=O bond is polar, leading to dipole dipole forces. The boiling points of esters are similar to ketones and aldehydes with similar relative molecular masses. The C=O polarity allows H bonding with water. Esters with fewer than 5 carbon atoms are water-soluble. Esters are soluble in non-polar solvents.

57
Q

What are the occurences and uses of esters?

A

Esters have a strong smell, usually pleasant. Ethyl ethanoate is found in mangoes. Ethyl ethanoate is also a solvent for paints. Lipids are long-chain carboxylic acids or esters.

58
Q

What is a secondary alcohol?

A

A secondary alcohol has 2 C atoms attached to the carbon with the hydroxyl group.

59
Q

What is a primary alcohol?

A

A primary alcohol has a carbon attached to the hydroxyl group which is bonded to one carbon atom.

60
Q

What is a free radicle?

A

A free radicle is an atom that has an unpaired electron.

61
Q

What is the industrial importance of ketones?

A

Propanone is used as a solvent in nail polish remover.

Chemistry (21 decks)

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