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2016 GAMSAT > Chemistry - Rings, Polymers and Analysis - F324 - Rings, Acids and Amines (1) > Flashcards

Chemistry - Rings, Polymers and Analysis - F324 - Rings, Acids and Amines (1) Flashcards

1
Q

What are arenes?

A

Arenes are aromatic carbons containing one or more benzene rings.

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2
Q

What are examples of natural sources of benzene?

A

Natural sources of benzene include volcanoes and forest fires.

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3
Q

Who suggested that there were two forms of benzene which were in rapid equilibrium?

A

Kekulé suggested that there were two forms of benzene which were in rapid equilibrium.

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4
Q

Who discovered that all the bonds in benzene were of the same length and bond angle?

A

Kathleen Lonsdale discovered that all the bonds in benzene were of the same length and their bond angle.

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5
Q

What is the bond angle of the bonds in benzene?

A

120o

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6
Q

What method did Kathleen Lonsdale use to make her discoveries?

A

X-ray diffraction

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7
Q

What length are all the bonds in benzene?

A

All of the bonds in benzene are 0.139nm

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8
Q

What length is a C-C single bond?

A

A C-C single bond is 0.153nm.

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9
Q

What length is a C=C double bond?

A

A C=C double bond is 0.134nm.

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10
Q

What is the enthalpy change of hydrogenation of a C=C double bond?

A

The enthalpy change of hydrogenation of a C=C double bond is -120kJmol-1.

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11
Q

What is the enthalpy change of hydrogenation of the bonds in benzene?

A

The enthalpy change of hydrogenation of a bond in benzene is -208kJmol-1

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12
Q

What about benzene’s structure make it more stable and less reactive?

A

The delocalised pi electrons above and below the plane of the benzene ring mean it is more stable.

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13
Q

What are the most common type (addition, substitution, elimination) of reactions in benzene chemistry?

A

Substitution reactions are the most common type of reaction in benzene chemistry.

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14
Q

What conditions does the nitration of benzene require?

A

Benzene will react with concentrated nitric acid and sulphuric acid (the catalyst) at 50oC

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15
Q

What is the catalyst in the reaction of benzene with nitric acid to nitrate the benzene ring?

A

Concentrated sulphuric acid is the catalyst in the nitration of benzene.

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16
Q

What happens in the nitration of benzene reaction if the temperature exceeds 50oC?

A

If the temperature exceeds 50oC then more than one nitro group is substituted onto the benzene ring.

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17
Q

What are the uses of nitrobenzene?

A

Nitrobenzene is an important starting material in the preparation of dyes, pesticides and pharmaceuticals.

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18
Q

Benzene will react with halogens in the presence of what?

A

Benzene will react with halogens in the presence of a halogen carrier, which is the catalyst.

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19
Q

Why do electrophilic substitution reactions take place in benzene?

A

Electrophilic substitution reactions take place because of the delocalised ring of electrons above and below the plane of carbon atoms.

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20
Q

In the nitration of benzene, what is the electrophile that the sulphuric acid helps generate?

A

The nitryl cation, or nitronium ion, which has the formula NO2+.

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21
Q

What are the phenols?

A

The phenols are a class of organic compound where the hydroxyl group is attached directly onto the benzene ring.

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22
Q

What state is phenol in at RTP?

A

Phenol is a solid at RTP.

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23
Q

What makes phenol slightly soluble in water?

A

The OH group can form hydrogen bonds with water making it slightly soluble.

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24
Q

What is formed when phenol is dissolved in water?

A

When phenol is dissolved in water, phenols form a weak acidic solution by losing an H+ from the OH group.

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25
Q

What is produced when a reactive metal is added to phenol?

A

The metal effervesces and hydrogen gas is given off.

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26
Q

What happens when bromine water is added to phenol?

A

The orange colour of bromine water disappears and a white precipitate is formed.

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27
Q

Why does bromine react more readily with phenol than with benzene?

A

Bromine reacts more readily with phenol because the lone pair on the oxygen is delocalised into the benzene ring creating a greater electron density able of polarising a bromine molecule.

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28
Q

What use did phenol have for many years?

A

Phenol (carbolic acid) was used as an antiseptic for many years.

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29
Q

What is the functional group found in aldehydes and ketones?

A

The C=O functional group is found in aldehydes and ketones.

30
Q

What is a suitable oxidising agent for primary and secondary alcohols?

A

Acidified dichromate ions (H+/Cr2O72-) are a suitable oxidising agent.

31
Q

Define reflux.

A

Reflux is the continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry.

32
Q

Carbonyl compounds can be reduced to alcohols using what reducing agent?

A

Carbonyl compounds can be reduced to alcohols using a reducing agent such as sodium tetrahydridoborate (III) NaBH4.

33
Q

Aldehydes and ketones react with NaBH4 in what type of reaction?

A

Aldehydes and ketones react with NaBH4 in nucleophilic addition reactions.

34
Q

Aldehydes and ketones can be detected using which reagent?

A

Aldehydes and ketones can be detected using the reagent 2,4-dinitrophenylhydrazine (2,4-DNP).

35
Q

What is 2,4-DNP made up of?

A

2,4-DNP is a mixture of methanol and sulphuric acid.

36
Q

What is 2,4-DNP also known as?

A

2,4-DNP is also known as Brady’s reagent.

37
Q

What happens when Brady’s reagent is added to an aldehyde or ketone?

A

When Brady’s reagent is added to an aldehyde or ketone then a yellow or orange precipitate is formed.

38
Q

Which reagent can be used to distinguish between aldehydes and ketones?

A

Tollen’s reagent can be used to distinguish between aldehydes and ketones.

39
Q

Tollen’s is a weak what?

A

Tollen’s is a weak oxidising agent.

It can oxidise aldehydes to carboxylic acids.

40
Q

What do you expect to see when Tollen’s is added to an aldehyde and a ketone?

A

When Tollen’s is added to an aldehyde a silver mirror is formed.
When Tollen’s is added to a ketone, nothing happens.

41
Q

How do you identify a 2,4-DNP derivative conclusively?

A

Filtered, recrystalised, allowed to dry, melting point is compared to a database.

42
Q

What chain length of carboxylic acid is soluble in water?

A

Short chain (1-4 carbons) carboxylic acids are very soluble in water.

43
Q

Salts formed from carboxylic acids are known as what?

A

Carboxylates are salts formed from carboxylic acids.

44
Q

What is esterification?

A

Esterification is the reaction of an alcohol with a carboxylic acid to produce an ester and water.

45
Q

What is often used as the catalyst in the preparation of esters?

A

Concentrated sulphuric acid is often used as the acid catalyst in the preparation of esters.

46
Q

How else may esters be produced, other than the reaction of an alcohol with a carboxylic acid?

A

Esters may also be produced by the reaction of an acid anhydride with an alcohol.

47
Q

Which method of ester production gives a better yield?

A

Heating an acid anhydride with an alcohol gives the best yield.

48
Q

In the reaction of acid anhydrides with alcohol to form an ester, what is the byproduct?

A

A carboxylic acid is the byproduct of the reaction of an acid anhydride with an alcohol.

49
Q

What conditions are required for acid hydrolysis of esters?

A

In acid hydrolysis, the ester is heated under reflux with dilute hydrochloric or sulphuric acid.

50
Q

What conditions are required for the alkaline hydrolysis of esters?

A

In alkaline hydrolysis of esters, aqueous sodium or potassium hydroxide is heated under reflux with the ester.

51
Q

What is/are the product(s) of acid hydrolysis of esters?

A

The alcohol and the carboxylic acid are the products.

52
Q

What is/are the product(s) of alkaline hydrolysis of esters?

A

Forms the sodium salt of the carboxylic acid and an alcohol.

53
Q

Is alkaline or acid hydrolysis of esters non-reversible?

A

Alkaline hydrolysis of esters is non-reversible.

54
Q

What are triglycerides made up of?

A

Triglycerides are triesters of propan-1,2,3-triol and three fatty acid molecules.

55
Q

In mono-unsaturated fatty acids, where is the double bond commonly found?

A

In mono-unsaturated fatty acids, the double bond is usually found between carbons 9 and 10.

56
Q

What is cis-trans isomerism?

A

Cis-trans isomerism is a special type of E/Z isomerism in which each carbon of the C=C double bond carries one atom or group that is the same.

57
Q

Do cis fatty acids usually exist as solids or liquids?

A

Cis fatty acids usually exist as liquids at room temperature.

58
Q

Why do cis fatty acids usually exist as liquids?

A

Cis fatty acids usually exist as liquids because they cannot pack closely together.

59
Q

What do low density lipoproteins (LDLs) do?

A

LDLs are responsible for carrying cholesterol and triglycerides from the liver to the tissues.

60
Q

What do high density lipoproteins (HDLs) do?

A

HDLs can remove cholesterol from the arteries and transport it back to the liver for excretion or re-utilisation.

61
Q

What is amphetamine used for?

A

Amphetamine is used to treat daytime drowziness and chronic fatigue syndrome.

62
Q

What is phenylephrine used for?

A

Phenylephrine is a decongestant.

63
Q

What is adrenaline used for?

A

Adrenaline is the fight or flight hormone.

64
Q

What is a primary amine?

A

A primary amine is one in which only one hydrocarbon chain attached to the nitrogen.

65
Q

What is a secondary amine?

A

A secondary amine is one in which the nitrogen atom is attached to two carbon chains.

66
Q

What is a tertiary amine?

A

A tertiary amine is one in which the nitrogen atom is attached to three carbon chains.

67
Q

Amines are what? (acids, alkalis, bases)

A

Amines are weak bases.

68
Q

What forms when an amine accepts a proton?

A

When an amine accepts a proton a dative covalent bond forms between the lone pair of the nitrogen and the proton.

69
Q

How are aliphatic amines generated?

A

Aliphatic amines can be prepared by gently warming halogenoalkanes with an excess of ammonia using ethanol as the solvent.

70
Q

How are nitrobenzene and other nitroarenes reduced?

A

Nitrobenzene and other nitroarenes can be reduced using a mixture of tin and concentrated HCl heated under reflux followed by neutralisation of the excess HCl.

71
Q

What are the two steps in the industrial preparation of dyes?

A

Diazotisation and coupling reactions

2016 GAMSAT (19 decks)

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