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Wrong Exam Qs > organic chem year 2👹👹👹 > Flashcards

organic chem year 2👹👹👹 Flashcards

1
Q

product when phenol reacts with bromine

observation

A

2,4,6-tribromophenol

white ppt
goes colourless

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2
Q

product when cyclohexene reacts with bromine

A

1,2-dibromocyclohexane

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3
Q

explain the relative resistance to bromination of benzene compared to phenol and compared to cyclohexene

A
  • benzene electrons are delocalised
  • phenol lone pair of electrons from oxygen are delocalised into ring
  • cyclohexane electrons are localised
  • benzene has lower electron density than phenol and cyclohexane
  • benzene cannot polarise Br2
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4
Q

difference in bonding between the two models of benzene

A

-p orbitals overlap

(in model with 3 double bonds)
-pi bonds localised

(in model with delocalised ring)
-pi bonds delocalised

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5
Q

ways to synthesise esters

A

carboxylic acid + 1 alcohol

acyl chloride + 1 alcohol

acid anhydride + 1 alcohol

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6
Q

how to name ester

A
  • second part refers to chain double bonded to oxygen

- first part refers to chain on other side of oxygen in the middle

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7
Q

for reaction between acid anhydride and alcohol

  • conditions
  • products
  • impact of each reactant on final product
A
  • no catalyst
  • ester and carboxylic acid
  • acid anhydride gives second chain with double oxygen bond
  • alcohol gives first section
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8
Q

for reaction between acyl chloride and alcohol

  • conditions
  • products
  • impact of each reactant on final product
A
  • no catalyst
  • ester and HCl
  • acyl chloride gives second chain with double oxygen bond
  • alcohol gives first chain
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9
Q

describe what is happening to the electron pairs in the first step of nucleophilic substitution (NaBH)

A
  • electron pair on H- is attracted to slightly positive carbon forming dative covalent bond
  • double electron pair breaks
  • electron pair now on O-
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10
Q

Butanal and butanone both react with 2,4-dinitrophenylhydrazine to produce mixtures containing orange precipitates.

Outline how the mixtures containing these orange precipitates can be used to distinguish between butanal and butanone.

A
  • recrystallise precipitate
  • measure melting point
  • compare with known values
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11
Q

Describe a simple chemical test that would show that but-2-enal is an
aldehyde.

A
  • heat with Tollens reagent

- silver mirror

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12
Q

Explain why Tollens reagent gives a different result with aldehydes than it does with ketones.

A
  • aldehydes can be oxidised to carboxylic acid

- aldehydes can reduce Ag+ to Ag

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13
Q

Tollens’ reagent can be used to identify the aldehyde group in cinnamaldehyde

Describe how you would make Tollens’ reagent and carry out this test in the laboratory.

Explain what happens to both the Tollens’ reagent and the cinnamaldehyde in this reaction. Identify the organic product.

A
  • silver nitrate and ammonia to make Tollens reagent
  • heat
  • silver mirror forms
  • Ag+ ions reduced
  • aldehyde oxidised to carboxylic acid
  • C6H5CHCHCOO-
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14
Q

products of reaction between nitrobenzene, tin and hydrochloric acid

A

phenylammonium chloride

water

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15
Q

products of reaction between phenylammonium chloride and sodium hydroxide

A

phenylamine

water

sodium chloride

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16
Q

phenol to hydroxypheylamine

A

HNO3

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17
Q

phenylammonium chloride to phenylamine

A

add NaOH

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18
Q

a mixture of tripeptides can be analysed by using gas chromatography, coupled with mass spectrometry.
Summarise how each method contributes to the analysis.

A

gas chrom- separates tripeptides

mass spec- produces distinctive fragmentation pattern

-identification by computer using spectral database

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19
Q

general formula of alpha amino acid

A

RCH(NH2)COOH

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20
Q

Explain what structural feature causes optical isomerism in organic molecules.

A
  • chiral
  • 4 different groups
  • mirror images cannot be superimposed
21
Q

Name a suitable reagent and conditions for the hydrolysis of polypeptide

A
  • aqueous HCl
  • under reflux
  • enzyme at 37 degrees
22
Q

state a use for a tough polypeptide

A
  • fire resistant clothing
  • tyres
  • tennis racket
23
Q

explain why branched chains have lower boiling point

A
  • less surface interaction between molecules
  • weaker london forces
  • require less energy to break
24
Q

Describe a method to obtain a pure sample of 3-nitrobenzoic acid from the impure solid and check purity

A
  • recrystallise
  • dissolve in hot water
  • cool solution and filter solid
  • wash with cold water and dry
  • find mp and compare with known values
  • pure will have mp close to data book value
25
Q

why is phenol easier to nitrate than benzoic acid

A
  • phenol has lone pair from o delocalised into ring
  • ring more susceptible to attack
  • benzoic acid has an electron withdrawing group
  • ring less susceptible to attack
26
Q

reduction of bromonitrobenzene reagents

A

Sn

HCl

27
Q

why does bromination of nitrobenzene and phenylamine put Br in different places

A

NH2 is 2,4 directing

28
Q

CN to COOH

A

aqueous H2SO4

29
Q

CN to CH2NH2

A

H2 Ni

30
Q

why does an amine form a salt with HCl

A

accepts proton

nitrogen has a lone pair

31
Q

why are condenstion polymers biodegradable (ester)

A

ester bond can be hydrolysed

32
Q

aldehyde to alcohol

A

NaBH4

33
Q

phenol reaction with na2co3

A

no reaction

34
Q

carboxylic acid reaction with na2co3

A

carbon dioxide produced

35
Q

State and explain how the halogen in the haloalkane affects the rate of hydrolysis

A
  • weaker bond= faster hydrolysis

- C-F bond is strongest so hydrolysed slowest

36
Q

aldehyde to CHOH(CN)

A

NaCN/H+

37
Q

CN + H+ forms

A

COOH

38
Q

NaOH reaction with OH and COOH

A

OH: O-Na+

COOH: COO-Na+

39
Q

Na2CO3 reaction with OH and COOH

A

OH: no

COOH: COO-Na+

40
Q

carboxylic acid to acyl chloride

A

PCl5

41
Q

why does hexane have a lower bp than heptane

A
  • heptane has more points of contact
  • heptane has more London forces
  • more energy needed to overcome forces
42
Q

why does a carboxylate salt need to be acidified in order for crystals to appear

A

protonates salt

43
Q

safety precaution with lead

A

wear gloves because lead is toxic

44
Q

test for phenol

A

Br2 makes white ppt

reacts with NaOH does not react with carbonates

45
Q

E/Z vs cis/trans isomers

A
  • in EZ all 4 groups can be different

- in cis trans at least 2 groups need to be the same

46
Q

why can a ring display only one of E or Z isomer

A

-the ring would have to break to display the other isomer

47
Q

what is the reference compound for NMR

A

tetramethylsilane

Si(CH3)4

48
Q

what solvent is used for NMR

A

CCl4

49
Q

what is D2O used for in NMR

A

makes the NH or OH peak disappear as the H exchanges with D

Wrong Exam Qs (41 decks)

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