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Chemistry A level > Organics > Flashcards

Organics Flashcards

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1
Q

How do you identify an alkane?

A

Hydrogen and carbon only (hydrocarbon) without double bond.

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2
Q

How do you identify an alkene?

A

Hydrogen and carbon only (hydrocarbon) with double bond.

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3
Q

How do you identify a free radical?

A

An unpaired electron on a molecule, noted with a black dot in formulae.

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4
Q

How do you identify a halogenoalkane?

A

Alkane with one halogen.

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5
Q

How do you identify a dihalogenoalkane?

A

Alkane with two halogens.

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6
Q

How do you identify an alcohol?`

A

Alkane with an OH group.

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7
Q

How do you identify a diol?

A

Alkane with 2 OH groups.

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8
Q

How do you identify a nitrile?

A

Alkane with C≢N.

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9
Q

How do you identify an amine?

A

Alkane with NH2.

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10
Q

How do you identify an aldehyde?

A

Alkane with double bonded O and H on end carbon.

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11
Q

How do you identify a carboxylic acid?

A

Alkane with double bond O and OH on end carbon.

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12
Q

How do you identify a ketone?

A

Alkane with double bond O no on end of carbon chain.

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13
Q

How do you identify an ester?

A

O=C-O-C in molecule / fruity smell

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14
Q

What are the different types of structural isomers?

A
  1. Chain
  2. Functional group - e.g. Hexane and hexene
  3. Position - e.g. double bond on 2nd instead of 3rd carbon
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15
Q

What is a homologous series?

A

A series of compounds with same functional groups and similar chemical properties.

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16
Q

What is geometrical isomerism? E-Z?

A

When isomers a different due to orientation. ONLY happens when a bond cant be rotated (pi bond). Pick heaviest group off each carbon and if same side then Z. If opposite then E.

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17
Q

What 3 reactions can alkanes do?

A

Combustion, Reforming, Cracking.

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18
Q

How do you get from alkane to halogenoalkane?

A

Using Free radical substitution with X2 under U.V.

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19
Q

How do you get from alkane to dihalogenoalkane?

A

Using Free radical substitution with X2 under U.V.

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20
Q

How do you get from alkene to alkane?

A

Electrophilic addition with H2 using Nickle catalyst

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21
Q

How do you get from alkene to halogenoalkane?

A

Electrophilic addition with HX

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22
Q

How do you get from alkene to dihalogenoalkane?

A

Electrophilic addition with X2

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23
Q

How do you get from alkene to diol?

A

Electrophilic addition with KMnO4 with H2SO4 (acidified)

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24
Q

How do you get from alkene to alcohol?

A

Electrophilic addition with steam

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25
Q

How do you get from halogenoalkane to amine?

A

Nucleophilic substitution with NH3 in ethanol/NaOH

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26
Q

How do you get from halogenoalkane to nitrile?

A

Nucleophilic substitution with KCN in ethanol

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27
Q

How do you get from halogenoalkane to alcohol?

A

Nucleophilic substitution with aqueous NaOH

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28
Q

How do you get from halogenoalkane to alkene?

A

Elimination with NaOH/KOH in ethanol

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29
Q

How do you get from alcohol to alkene?

A

Elimination with conc. H3PO4

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30
Q

How do you get from alcohol to Ketone?

A

Oxidation of secondary alcohol with K2Cr2O7 and H2SO4 (acidified dichromate)

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31
Q

How do you get from alcohol to aldehyde?

A

Oxidation of primary alcohol with K2Cr2O7 and H2SO4 (acidified dichromate)

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32
Q

How do you get from aldehyde to carboxylic acid?

A

Oxidation with K2Cr2O7 and H2SO4 (acidified dichromate)

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33
Q

How do you get from alcohol to ester?

A

Condensation(forms water) with carboxylic acid and H2SO4.

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34
Q

How do you get from carboxylic acid to ester?

A

Condensation with alcohol and H2SO4.

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35
Q

What are the three steps of a reaction?

A
  1. Initiation
  2. Propagation
  3. Termination
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36
Q

What reactions do alkenes always do?

A

Addition

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37
Q

What is an electrophile and give 2 examples.

A

An electrophile is something which is attracted to electron-rich regions in other molecules or ions. E.g. HX or X2

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38
Q

What is a neucleophile and give 2 examples.q

A

Something attracted to a positive charge (nucleus) in other molecules or ions. E.g. OH- or NH3

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39
Q

What is a positive inductive effect?

A

The electrons are pushed making the positive charge on Carbon smaller and MORE STABLE. E.g. CH3 groups or metals

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40
Q

What is a negative inductive effect?

A

Electrons are pulled towards a group increasing positive charge and making a LESS STABLE charge. E.g. F, O, N.

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41
Q

For neucleophilic substitution, how do you know if it is SN1 or SN2?

A

SN1 is tertiary halogenoalkanes.
SN2 is primary halogenoalkanes due to steric hinderence from methyl groups.
Secondary can do both.

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42
Q

Does SN1 or SN2 have a transition stage?

A

SN2 has a transition stage. SN1 is slow as it breaks without another molecule.

43
Q

What is steric hindrance?

A

Molecules being crowded meaning a reaction can’t take place.

44
Q

How do you decide a mechanism based on polarity and double bonds?

A

Polar = neucleophilic
Non-polar = Electrophilic
Double bond = Addition
No double bond = Substitution

45
Q

What do you get from oxidising a tertiary alcohol?

A

You can’t oxidise a tertiary alcohol as there is no second hydrogen on the carbon to remove with the hydrogen in OH group

46
Q

In SN2 reaction how far apart are the nucleophiles in transition stage?

A

180 degrees

47
Q

What are the four definitions of oxidation?

A
  1. Loss of electrons
  2. Gain of oxygen
  3. Loss of hydrogen
  4. Gain in oxidation state
48
Q

What is the colour change when acidified dichromate (VI) reacts with primary or secondary alcohol?

A

Orange –> Green.

No colour change for tertiary

49
Q

What does PCl5 test for?

A

OH group forms steamy white fumes (HCl gas)

50
Q

What is the test for carbonyl group (Aldehyde/ketone)? Method and results?

A

2,4 - dinitrophenyl hydrosine. Add 2,4-dnp to drops of carbonyl. Positive test for aldehyde is due to aldehyde being oxidised and Cr2O7 2- is reduced forming yellow/orange ppt in condensation reaction. Ketone doesn’t form ppt. .

51
Q

What technique should you use to collect carboxylic acid?

A

Reflux (condenser on top of heat)

52
Q

What is formed from halogenoalkane if KCN or NH3 are aqueous?

A

An Alcohol

53
Q

What is an initiation stage?

A

Molecule –> 2F.R.

54
Q

What is a propagation stage? Give 2 examples for CH4 + Br2 –> ChH3BR reaction

A

1 molecule + 1F.R. –> F.R. + molecule

  1. Br• + CH4 –> •CH3 + HBr
  2. •CH3 + Br2 –> CH3Br + Br•
55
Q

What is a termination stage?

A

2F.R. –> Molecule

56
Q

How do you get from Alcohol to Halogenoalkane?

A

Nucleophilic substitution with Conc. H2SO4
+ PCl5 for chloroalkane
+ KBr for Bromoalkane
+ I2 and Phosphorus for Iodoalkane

57
Q

What is heterolytic or homolytic bond breaking?

A

Heterolytic - bond breaking connecting to different species

Homolytic - same species

58
Q

How do you test for an alkene?

A

Bromine or bromine water goes colourless.

59
Q

What type of stereo isomerism is there?

A

Geometrical and Optical

60
Q

What are optical isomers? and why do they occur?

A

They are isomers which have a chiral centre meaning they have mirror images.

61
Q

What is a racemic mixture?

A

When there is a 50;50 mix of two optical isomers rotating a polarised plane of light equally in opposite directions.

62
Q

Can SN1 or SN2 form optical isomers?

A

Only SN1 as SN2 has too much steric hindrance for the nucleophile to attach to both sides.

63
Q

How would you identify a carbonyl with 2,4-dnp?

A

Add a few drops of 2,4-dnp to the carbonyl. Orange ppt forms. Purify it by filtering and washing. Then measure melting point and check in data book to see which aldehyde or ketone.

64
Q

Explain the method and results for Tollen’s/Ammonial silver nitrate test.

A

Add NaOH to silver nitrate and then ammonia to dissolve the silver oxide. Then add 5 drops of carbonyl and heat gently. A positive test for aldehyde gives a silver mirror. Ketone doesn’t. This is because aldehydes can be oxidised, reducing the silver ion.

65
Q

Explain the method and results for Fehling’s solution?

A

Add a few drops of carbonyl to reagent and heat gently. Positive tests for red ppt as aldehydes oxidise, reducing the copper ion. Ketone doesn’t show this.

66
Q

Explain the method and results for Iodoform test?

A

Add NaOH with drops of carbonyl. Add iodine until faint brown colour. Test is for methyl ketone or ethanal. Positive forms pale yellow ppt.

67
Q

How do you get from aldehyde/ketone to hydroxynitrile?

A

Neucleophilic addition with KCN to get CN- then HCN from then on.

68
Q

How do you identify a hydroxy nitrile?

A

An alkane with a nitrile and OH group.

69
Q

How do you from grignard reagents?

A

Halegenoalkane + Mg —> R- + MgBr- . Catalyst dry ether.

70
Q

What 5 reactions can grignards do?

A
  1. With water forms alkane and Mg(OH)Br.
  2. With methanal forms primary alcohol and Mg(OH)Br.
  3. With aldehydes forms secondary alcohol and Mg(OH)Br.
  4. With Ketone forms tertiary alcohol and Mg(OH)Br.
  5. With CO2 forms carboxylic acid.
71
Q

How do you get from Grignard to carboxylic acid?

A

React with CO2 in dry ether.

72
Q

How do you get from a nitrile to carboxylic acid?

A

Hydrolosis with acid or alkali.

  • Alkali is more efficient and goes to completion but forms an ethanoate ion before being reacted with strong acid to form carboxylic acid.
  • Acid immediately forms product
73
Q

Explain the mtp of carboxylic acids?

A

They are liquids/solids at RTP as all can hydrogen bond. Although lower than water as only one hydrogen bond. Longer chains = more london forces = higher mtp

74
Q

Explain the solubility of carboxylic acids?

A

Longer C chains = less soluble in water (as less polar)

75
Q

Explain recrystallisation purification technique?

A

Use solvent where product is soluble hot and insoluble cold.

  1. Dissolve compound in minimum amount of hot solvent.
  2. Filter whilst hot.
  3. Cool to crystallise.
  4. Filter and dry compound on paper.
  5. Wash and leave to fully dry.
76
Q

How do you get from carboxylic acid to salt?

A

React with metal/carbonate/base.

77
Q

How do you get from carboxylic acid to aldehyde?

A

Reduction with LiAlH4 (reducing agent) and dry ether.

78
Q

How do you get from aldehyde to primary alcohol?

A

Reduction with LiAlH4 (reducing agent) and dry ether.

79
Q

How do you get from carboxylic acid to Acyl chloride?

A

Nucleophilic substitution with PCl5 to form Acyl Chloride + POCl3 + HCl(steamy white fumes)

80
Q

What is a test for Carboxylic acids vs Alcohols?

A

Add Na2CO3, Carboxy fizzes due to CO2, alcohol doesn’t

81
Q

How do you get from carboxylic acid to primary alcohol?

A

Reflux with LiAlH4 in condensation reaction

82
Q

How do you get from Acyl chloride to ester?

A

Condensation with alcohol to form Ester and HCl.

83
Q

How do you get from acyl chloride to carboxylic acid?

A

Hydrolysis with water to form carboxylic acid and HCl

84
Q

What happens in hydrolysis of an ester with water?

A

Hydrolysis (react with water) acid catalyst to form carboxylic acid and alcohol under reflux. V slow

85
Q

What happens in hydrolysis of an ester with dilute alkali?

A

Forms a salt of carboxylic acid (sodium propanoate) and alcohol under reflux. Form carboxylic acid by adding excess HCl to the salt.

86
Q

Why is hydrolysis of an ester using alkali rather than water advantageous?

A

Alkaline one is not reversible.

Alkaline one is easier to separate products. Although doesn’t form carboxylic acid initially.

87
Q

How do you get from acyl chloride to substituted amide?

A

Condensation with an amine to form a substituted amide.

88
Q

How do you get from acyl chloride to amide?

A

Condensation with ammonia (NH3) to form amide and HCl.

89
Q

How do you identify an amide?

A

Alkane with group -CONH2, O is double bonded.

90
Q

How do you identify a substituted amide?

A

Amide with a methyl group in place of a hydrogen.

91
Q

How do you form a polyester by condensation?

A

React two molecules with two OH groups and COOH group (e.g. 2-hydroxy propanoic acid) with an acid. Forms water.

92
Q

Why is it advantageous to form ester from carboxylic via acyl chloride than directly?

A

It is quicker and goes to completion via acyl chloride.

93
Q

What is benzene?

A

C6H6 with delocalised pi electrons and all carbon bonds the same length.

94
Q

How do you get from Ketone to Alcohol?

A

Reduction with LiAlH4 in dry ether

95
Q

How do you get from Amine to Amide?

A

Condensation with acyl chloride

96
Q

How do you get from Nitrile to Amine?

A

Electrophilic addition with HCl

97
Q

How do you get from 2-hydroxy nitrile to a 2-hydroxy carboxylic acid?

A

Hydrolysis with alkaline or acid.

98
Q

How do you get from carboxylic acid to ester?

A

Alcohol + H2SO4

99
Q

What reactions do Benzene rings do?

A

Electrophilic addition

100
Q

How do you get from benzene to chlorobenzene?

A

In Friedel-Craft halogenation, use AlCl3 and Cl2 to form Cl+ in dry ether. Then electophilic addition for benzene to chlorobenzene, HCl and AlCl3.

101
Q

How do you get from benzene to nitrobenzene?

A

Use conc. HNO3 and conc. H2SO4 to form NO2+. At 55 degrees.

102
Q

How do you get from benzene to methyl benzene?

A

Form CH3+ from R-Cl + AlCl3 in dry ether. Then electophilic addition with benzene to form HCl and AlCl3.

103
Q

How do you get from nitrobenzene to phenylbenzene?

A

Electrophilic addition with conc. HCl and Sn.

104
Q

How do you get from benzene to benzaldehyde?

A

React acyl chloride + AlCl3 to form HCO+ in dry ether. Then react with benzene to form benzaldehyde, HCl and AlCl3.

Chemistry A level (6 decks)

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