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A Level Chemistry- CAIE > Organic Chemistry (AS and A2) > Flashcards

Organic Chemistry (AS and A2) Flashcards

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1
Q

What are the conditions for the addition of hydrogen to an alkene?

A

Hydrogen and a finely divided nickel catalyst at 140 C. Alkane produced.

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2
Q

What are the conditions for the addition of steam to an alkene?

A

Concentrated phosphoric acid at 330 C and 6 MPa. Alcohol produced.

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3
Q

What are the conditions for the addition of a hydrogen halide to an alkene?

A

A concentrated solution of the hydrogen halide at room temperature. Halogenoalkane produced.

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4
Q

What are the conditions for the addition of a halogen to an alkene?

A

Bubble the alkene through a solution of the halogen at room temperature. Bromine water is decolourised. Halogenoalkane produced.

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5
Q

What are the conditions for the oxidation of an alkene to a diol?

A

Cold dilute solution of acidified potassium manganate (VII).

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6
Q

H2C=C is oxidised by hot, concentrated acidified potassium manganate (VII) solution. What is one of the products?

A

CO2

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7
Q

RHC=C is oxidised by hot, concentrated acidified potassium manganate (VII) solution. What is one of the products?

A

RHC=O, an aldehyde. Further oxidation to RCOOH, carboxylic acid.

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8
Q

R2C=C is oxidised by hot, concentrated acidified potassium manganate (VII) solution. What is one of the products?

A

R2C=C, a ketone

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9
Q

How can you convert a halogenoalkane to an alcohol?

A

Reflux with OH-, water or NaOH. This is nucleophilic substitution.

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10
Q

What are the conditions for the nucleophilic substitution of CN- into a halogenoalkane?

A

KCN in ethanol, heated under reflux. Halogen replaced with CN to form nitrile.

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11
Q

What are the conditions for the nucleophilic substitution of ammonia into a halogenoalkane?

A

Excess of hot ammonia dissolved in ethanol under pressure. Halogen replaced by NH2 to form amine and HBr. HBr reacts with the ammonia to form NH4Br.

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12
Q

What are the conditions for the elimination reaction for a halogenoalkane?

A

Ethanolic NaOH and heat. The products are an alkene, water and a hydrogen halide.

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13
Q

What are the conditions for the nucleophilic substitution of a halogen into an alcohol?

A

Alcohol is heated under reflux. Reagent is either a hydrogen halide, sulfur dichloride oxide, phosphorus (V) chloride, phosphorus (III) halide (only warming needed). Halogenoalkane produced. Equations on page 228.

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14
Q

What are the products when an alcohol is reacted with sodium?

A

Sodium alkoxide and Hydrogen.

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15
Q

Outline the conditions for esterification.

A

Acid catalyst (usually concentrated sulfuric acid), heated under reflux, reaching an equilibrium. First part of the ester’s name comes from the alcohol.

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16
Q

Outline the conditions for the hydrolysis of an ester.

A

Refluxing with acid produces the alcohol and the carboxylic acid in equilibrium. Refluxing with excess alkali, an alcohol and a sodium salt is formed (no equilibrium).

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17
Q

What are the conditions for the dehydration of an alcohol?

A

Alkene and water produced. Alcohol vapour is passed over a hot catalyst of aluminum oxide powder. Pieces of porous pot or pumice can be used instead.

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18
Q

Outline the oxidation of alcohols.

A

Oxidised by warmed potassium dichromate (VI) solution, acidified with dilute sulfuric acid. Tertiary alcohols, no reaction. Secondary alcohols, ketone and water. Primary alcohol forms an aldehyde. The aldehyde can be oxidized to a carboxylic acid. Aldehyde needs to be distilled off to prevent further oxidation.

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19
Q

What are the conditions for the conversion of a nitrile to a carboxylic acid?

A

A nitrile is refluxed with dilute hydrochloric acid (water is also a reagent in the equation). Ammonium chloride is produced along with the carboxylic acid.

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20
Q

What are the conditions for the reduction of a carboxylic acid?

A

LiAlH4 in dry ether at room temperature. An alcohol and water is produced.

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21
Q

Briefly explain why the benzene molecule is planar?

A

Because the carbons are joined by pi bonds.

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22
Q

Briefly explain why all the carbon-carbon bonds in benzene are the same length.

A

Because the pi electrons are delocalised.

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23
Q

Describe the bonding and shape of a molecule of benzene.

A

Each carbon atoms forms three sigma bonds (2 C-C and one C-H).
Carbons are sp2.
Rings of charge above and below the ring (lobes of the p orbitals form to form a ring of delocalised electrons).
The six electrons in the pi bonds are delocalised.
Planar molecule of bond agle 120 degrees
All C-C are the same length.

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24
Q

Why do ethene and benzene differ in their reaction with bromine?

A

Delocalised ring of electrons in benzene is stable, so is reformed in step after intermediate.

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25
Q

What are the conditions for the electrophilic substitution of benzene with chlorine or bromine?

A

Page 384 for the mechanism.
Catalyst: anhydrous iron (III) bromide, iron (III) chloride or aluminium chloride.
Pure halogen gas (not a solution) is bubbled through benzene.

26
Q

How is chloromethylbenzene formed?

A

Methylbenzene reacted with chlorine in the presence of UV light. HCl is also formed.

27
Q

What are the conditions for the electrophilic substitution/nitration of benzene?

A

Page 385 for the mechanism.
55 C, concentrated nitric acid and sulfuric acid, reflux.
Nitronium ion is the electrophile.
HNO3 + 2H2SO4 = NO2+ +2HSO4- +H30+

28
Q

Define Fidel-Crafts reaction.

A

Reactions resulting in the introduction of a side-chain into a benzene ring.

29
Q

Outline Fidel-Crafts reaction.

A

AlCl3 catalyst.
Page 386 for the mechanism.
Benzene + chloroethane = ethylbenzene + HCl (alkylation)
Benzene + ethanoyl chloride = phenylethanone + HCl
Page 386

30
Q

What are the conditions for the oxidation of the side-chain in arenes?

A

All side chains oxidised to benzoic acid.
Reflux with alkaline potassium manganate (VII), and then acidified with dilute sulfuric acid or another strong oxidising agent like acidified potassium dichromate (VI)

31
Q

Describe the acidities of water, ethanol and phenol.

A

Phenol is the most acidic, ethanol is the least acidic.
The phenoxide ion is the most stable as its negative charge is spread over the whole ion as one of the lone pairs on the oxygen atom overlaps with the delocalised pi bonding system in the benzene ring. Lower charge density of negative charge H+ ions not as strongly attracted to phenoxide ion.
Ethanol is a weaker acid than water because of the electron-donating ethyl group attached to the oxugen atom in the ethoxide ion. More negative charge on the oxygen, readily accepts an H+ ion.

32
Q

Describe the reactions of phenol with NaOH and Na.

A

Cold/room temperature

Phenol reacts like an acid forming a sodium salt and water or hydrogen.

33
Q

What are the conditions for the bromination of phenol?

A

React with bromine water at room temperature. 2,4,6-tribromophenol and HBr is formed.

34
Q

What are the conditions for the nitration of phenol?

A

React with dilute nitric acid at room temperature. 2-nitrophenol and 4-nitrophenol is formed. If concentrated nitric acid is used 2,4,6-trinitrophenol is produced.

35
Q

Describe the acidity of carboxylic acids.

A

The OH bond in the carboxylic acid is weakened as the electrons in the CO bond are drawn towards the C=O bond and away from the OH bond.
The carboxylate ion is stabilized by the delocalisation of the electrons around the COO- group. The negative charge is spread out on the carboxylate ion, reducing its charge density and making it less likely to bond with an H+ ion.

36
Q

The more chlorines in a carboxylic acid, the stronger the acid. Why?

A

Chlrine is an electron-withdrawing group. The more chlorine atoms, the greater the stabilising effect on the anion, spreading the negative charge more, weakening the OH bond in the acid.
Ethanoic acid is weaker than the chlorine substituted carboxylic acids because the methyl group is electron donating, strengthens the OH bond, donated charge towards the COO- group, making it more likely to accept an H+ ion.

37
Q

Outline the reduction of aldehydes and ketones.

A

Aldehyde + reducing agent = primary alcohol
Ketone + reducing agent = secondary alcohol
The reduction reaction is carried out by either:
Warming the aldehyde or ketone with an aqueous alkaline solution of sodium tetrahydridoborate NaBH4.

Adding lithium tetrahydridoaluminate LiAlH4, in dry ether at room temperature.

38
Q

What are the conditions for the nucleophilic addition of HCN to an aldehyde or ketone?

A

HCN generated in situ by the reaction of NaCN and dilute sulfuric acid. NaCN then acts as a catalyst. Addition of HCN takes place across the C=O bond. Propanal + HCN = 2-hydrocybutanenitrile page 238

39
Q

What are the conditions for the reduction of a nitrile group to an amine?

A

The nitrile vapour and hydrogen gas is passed over a nickel catalyst or LiAlH4 in dry ether.

40
Q

Describe the test for a carbonyl group.

A

Add a solution of 2,4-DNPH. If an aldehyde or ketone is present, a deep orange precipitate is formed. This is a condensation reaction.

41
Q

Describe the test with Tollens’ reagent.

A

Tollens’ reagent is an aqueous solution of silver nitrate in excess ammonia solution. When an aldehyde is present and warmed with Tollens’ reagent, a silver mirror is formed. Methanoic acid also gives a positive result.

42
Q

Describe the test with Fehling’s solution.

A

When warmed with an aldehyde, the clear blue solution turns an opaque red/orange colour. Methanoic acid also gives a positive test.

43
Q

Describe the reactions to form tri-iodomethane.

A

Tri-iodomethane forms as a ppt with methyl ketones (CH3CO-), ethanal CH3CHO and CH3CH(OH)- (secondary alcohol with a methyl group at one end). The reagent used is an alkaline solution of iodine which is warmed together with the substance being tested.

44
Q

What are the conditions for the oxidation of methanoic acid?

A

Acidified solution of potassium manganate (VII) or potassium dichromate (VI) or Tollens’ regent or Fehling’s solution, the last two are mild oxidising agents. CO2 and H2O are the only products.

45
Q

What is an acyl chloride?

A

OH group in a carboxylic acid is replaced with Cl.

46
Q

What is the equation for the reaction of carboxylic acid with PCl5?

A

Carboxylic acid + PCl5 = Acyl chloride + POCl3 + HCl

47
Q

What is the equation for the reaction of carboxylic acid with PCl3?

A

3 Carboxylic acid + PCl3 = 3 Acyl chloride + H3PO3

Heat.

48
Q

What is the equation for the reaction of carboxylic acid with SOCl2?

A

Carboxylic acid + SOCl2 = Acyl chloride + SO2 + HCl

49
Q

Explain the reactivity of acyl chlorides.

A

The carbonyl carbon has electrons drawn away from it by the Cl atoms as well as by its O atom, and both are strongly electronegative atoms. This gives the carbonyl carbon a relatively large partial positive charge and makes it particularly open to attack from nucleophiles.

50
Q

Describe the reaction of acyl chlorides with HZ.

A

HZ can be water, an alcohol, ammonia or an amine. HZ acts as a nucleophile. With water, the reaction is hydrolysis- acyl chloride becomes a carboxylic acid, HCl is also produced. White fumes (HCl). Room temperature. Mechanism on page 397.

51
Q

Describe the reactivities of Acyl chlorides, chloroalkanes and Aryl chlorides.

A

Acyl chloride the most reactive, Aryl chlorides the least reactive. Acyl chloride has two electron-withdrawing groups, making the carbon more partially positive and open to nucleophilic attack. Meanwhile, for aryl chlorides (they don’t undergo hydrolysis). The p orbitals from the Cl atom tend to overlap with the delocalised p electrons in the benzene ring. C-Cl bond has some double bond character, making it stronger.

52
Q

Describe the reaction of acyl chlorides with ethanol.

A

Acyl chloride more reactive than carboxylic acid. Reacts with alcohols to form an ester and HCl (no equilibrium like with carboxylic acid). This is room temperature.
Acyl chloride needs to be warmed with phenol. There is no reaction between phenol and carboxylic acids, but with acyl chloride the reaction takes place in the presence of a base. Phenol reacts with the base, like NaOH to form sodium phenoxide. Sodium phenoxide reacts with the acyl chloride to form the ester. The acyl chloride can have a benzene ring, like benzoyl chloride. A salt, like NaCl is formed. Page 398

53
Q

Describe the nucleophilic substitution reaction of acyl chloride with an amine.

A

A substituted amide and HCl is formed. CH3COCl + CH3NH2 = CH3CONHCH3 + HCl
Acyl chloride can also react with ammonia to form an amide. Room temperature. If there is an excess of amine, it reacts with HCl to make its salt.

54
Q

Describe and explain how the basicities of ammonia, ethylamine and phenylamine differ.

A

Ethylamine is the strongest base, phenylamine is the weakest base from the three. In ethylamine, the alkyl group donates electrons to the N, making the lone pair more available. Electron density of N is increased. In phenylamine, the lone pair is delocalised over the ring, so is less available. Electron density of N is reduced.

55
Q

Explain why ethylamine is basic.

A

Contains a lone pair on N that can react with H+.

56
Q

Describe the reduction of amide.

A

LiAlH4 in dry ether reduces amides to amine. H2O also formed. Page 403

57
Q

What are the conditions for the preparation of phenylamine?

A

Phenylamine is made by reducing nitrobenzene. Page 403. Heat nitrobenzene with tin and concentrated hydrochloric acid. Water is also formed. Phenylamine is separated from the reaction mixture by steam distillation.

58
Q

What are the conditions for the electrophilic substitution of bromine into phenylamine?

A

Bromine water, room temperature. 2,4,6-tribromophenylamine is formed. 3HBr is formed.

59
Q

Outline the reactions between phenylamine and nitrous acid.

A

Nitrous acid decomposes very readily and is always made in situ. In the case of its reaction with phenylamine, the phenylamine is first dissolved in hydrochloric acid, and then a solution of sodium or potassium nitrite is added. The reaction between the hydrochloric acid and the nitrite ions produces the nitrous acid.
Phenylamine reacts with nitrous acid differently depending on the temperature.
If the mixture is warmed, you get a black oily product which contains phenol (amongst other things), and nitrogen gas is given off.
C6H5NH2 + HNO2 = C6H5OH + H2O + N2
The reaction at low temperatures

The solution of phenylamine in hydrochloric acid (phenylammonium chloride solution) is stood in a beaker of ice. The sodium or potassium nitrite solution is also cooled in the ice.

The solution of the nitrite is then added very slowly to the phenylammonium chloride solution - so that the temperature never goes above 5°C.

You end up with a solution containing benzenediazonium chloride (PICTURE ON 403).

The positive ion, containing the -N2+ group, is known as a diazonium ion.

Ionic equation on page 404.

60
Q

Describe a zwitterion and how it resists changes in pH.

A

Zwitterion carries two charges. Ionic nature of zwitterion gives relatively strong intermolecular forces. They are crystalline solids soluble in water. They are amphoteric. If acid is added COO- becomes COOH. If alkali is added NH3+ becomes NH2 and water.

61
Q

Outline the hydrolysis of amides.

A

The amide is refluxed with hydrochloric acid to form RCOOH and RNH2. Excess H+ forms RNH3+ (ammonium salt with the acid)

Refluxing with an alkali, eg, aq NaOH, the products are the sodium salt of the carboxylic acid (RCOONa) and the primary amine (RNH2)

If we reflux with an unsubstituted amide (RCONH2) with an acid, the products are the corresponding carboxylic acid and ammonia. Ammonia reacts with the acid to form an ammonium salt. With an alkali, the products are the salt of the carboxylic acid and ammonia.

A Level Chemistry- CAIE (1 decks)

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