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Chemistry Year 12/13 > Module 6.2 - Nitrogen Compounds, Polymers and Synthesis > Flashcards

Module 6.2 - Nitrogen Compounds, Polymers and Synthesis Flashcards

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1
Q

What are the 3 types of amine and what is each one?

A
  • primary amine: 1 H has been substituted, RNH2
  • secondary amine: 2 H’s have been substituted, RNHR’
  • tertiary amine: all 3 H’s have been substituted, RNR’R’’
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2
Q

How do you name primary amines?

A

Determine root by longest hydrocarbon chain. Add any prefixes/other groups then add suffix ‘amine’

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3
Q

How do you name secondary amines?

A
  • determine root by naming 2 alkyl chains
  • add any prefixes for additional groups and write them alphabetically
  • add suffix amine
  • as alkyl groups attached to N atom, secondary amines are N-substituted, given as a prefix to the name
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4
Q

How do you name tertiary amines?

A
  • determine root by naming 3 alkyl chains
  • di or tri if many of the same one
    e. g. N-diethylpropylamine
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5
Q

What is a Lewis base?

A

Has a lone pair of electrons for donation. Ammonia and amines have a lone pair of electrons on the nitrogen atom, making them a Lewis base

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6
Q

What is a Brønsted-Lowry base?

A

Proton acceptor, ammonia and amines can accept protons on nitrogen atom, making them a Brønsted-Lowry base

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7
Q

Using the Brønsted-Lowry model of bases, how can ammonia/amines act as a base?

A
  • weak bases
  • amine accepts a proton when it reacts w acid
  • covalent bond is formed by N atom donating its lone pair of electrons to proton to form a dative covalent (coordinate) bond
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8
Q

What is an alkylammonium salt?

A

A compound where the hydrogen(s) on an ammonium ion have been substituted for alkyl chains

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9
Q

Describe the reaction between (primary?) amines and dilute hydrochloric acid.

A
  • HCl is a strong inorganic acid and fully ionises in solution
  • when HCl(aq) reacts w a base, a chloride salt and water are produced
  • when primary amines react w HCl, an alkylammonium salt is formed (from the proton in the acid being replaced by the alkylammonium ion).
    e. g.

CH3CH2NH2 + HCl → CH3CH2NH3+Cl- (alkylammonium chloride)

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10
Q

Describe the reaction between (primary?) amines and dilute dilute nitric acid

A

CH3CH2NH2 + HNO3 → CH3CH2NH3+NO3- (alkylammonium nitrate)

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11
Q

Describe the reaction between (primary?) amines and dilute sulfuric acid?

A

2CH3CH2NH2 + H2SO4 → [CH3CH2NH3+]2SO42- (alkylammonium sulfate)

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12
Q

How would you prepare aliphatic amines?

A
  • sealed tube, haloalkane, ammonia and ethanol are heated together to make an amine (reflux can’t be used as ammonia is so volatile it would escape condenser rather than react)
  • haloalkane (e.g. 1-chloropropane) undergoes nucleophilic substitution in 2 stage process to form primary amine
  • Stage 1: ammonia reacts w haloalkane to make ammonium salt, CH3CH2CH2Cl + NH3 → CH3CH2CH2NH3Cl
  • Stage 2: additional ammonia molecules react to form propylamine product and NH4Cl (reversible so ammonia will drive reaction to RHS increasing yield of primary amine, CH3CH2CH2NH3Cl + NH3 ⇌ CH3CH2CH2NH2 + NH4Cl
  • additional substitution of H atoms on N can occur, initially N-dipropylamine (secondary amine) is formed: CH3CH2CH2NH2 + CH3CH2CH2Cl ⇌ (CH3CH2CH2)2NH + HCl
  • further substitution produces N-tripropylamine (tertiary amine): CH3CH2CH2Cl + (CH3CH2CH2)2NH ⇌ (CH3CH2CH2)3N + HCl
  • final stage produces a quaternary ammonium salt, where each H on ammonium ion has been replaced by an alkyl chain: CH3CH2CH2NH3Cl + (CH3CH2CH2)3N ⇌ (CH3CH2CH2)4N+Cl-

(-further substitutions occur as amines have lone pairs of electrons that can act as a nucleophile)

  • mixture of products produced
  • as second stage is in equilibrium excess ammonia favours primary amine and excess haloalkane favours quaternary ammonium salt
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13
Q

How would you prepare aromatic amines?

A
  • nitroarenes (e.g. nitrobenzene) can be reduced to amines
  • reducing agent is made in situ using a mixture of tin and conc HCl
  • reaction occurs under reflux at 100°C
  • after about half an hour, a strong alkali e.g. NaOH is added. Undergoes a neutralisation reaction to remove excess HCl and produce the amine. Separating the aromatic amine is a multistage process including steam distillation, solvent extraction and further distillation
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14
Q

What is the general structure of an α-amino acid and how do amino acids react because of it?

A

RCH(NH2)COOH

  • both functional groups (-NH2 and -COOH) are attached to the same carbon atom
  • partially ionises in water
  • N has a lone pair of electrons so can act as a base
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15
Q

Amino acids are amphoteric. What does this mean and how are amino acids amphoteric?

A
  • can act as a base and an acid
  • base from lone pair of electrons on nitrogen atom
  • acid from acidic carboxyl group
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16
Q

How does an amino acid form a zwitterion?

A
  • proton from carboxylic acid group donated to basic amine group to make an internal salt
  • the 2 charges cancel each other out, so there’s no overall charge
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17
Q

What is the isoelectric point of a zwitterion?

A

When there is no net electrical charge due to each zwitterion having an internal balance of charge. Changing the pH alters the amino acids so only 1 functional group is charged

18
Q

How does pH affect the charge balance in an amino acid zwitterion?

A
  • isoelectric point: no charge as the charges on the carboxylic acid and amine groups cancel out
  • acidic solution (high H+ conc): positive charge, basic amine group accepts a proton but carboxylic acid group doesn’t lose its proton
  • alkaline soltion (high OH- conc): negative charge, carboxylic acid group donates H+ to OH- group to form H2O
19
Q

Describe the reaction between amino acids and metal oxides.

A
  • carboxylic acid functional group
  • metal oxides are bases so a neutralisation reactino occurs
  • H from carboxylic acid exchanged for a metal ion to produce a metal salt
  • water also produced
20
Q

Describe the reaction between amino acids and alkalis.

A
  • carboxylic acid group
  • alkalis are soluble bases so a neutralisation reaction occurs
  • produces a salt and water
21
Q

Describe the reaction between amino acids and carbonates.

A
  • carboxylic acid group
  • neutralisation reaction
  • produces salt, water and CO2 gas (effervescence)
22
Q

Describe the reaction between amino acids and alcohols.

A
  • carboxylic acid functional group
  • produes an ester
  • releases a molecule of water
23
Q

Describe the reaction of amino acids as bases e.g. with acids.

A
  • amine group
  • acts as a base due to lone pair of electrons on nitrogen atom
  • when acid added to amino acid, amine group accepts a proton
  • forms an ammonium salt
24
Q

What is an amide?

A

A class of compound with a functional group of an acyl group, which is directly attached to an amine, RC(O)NH2

25
Q

How do amides compare to carboxylic acids?

A

Amides have hydroxyl group substituted for an amide group

26
Q

How do amide compare to ammonia?

A

Amides are ammonia where one or more H have been substituted for an acyl group

27
Q

What are the different types of amides?

A
  • primary amide: N atom has 2 H atoms and one acyl group attached
  • secondary amide: N atom has 2 H atom, one acyl group and one alkyl group attached
  • tertiary amide: N atom has no H atoms attached
  • polyamide: type of condensation polymer, v long chain molecule, repeating pattern of atoms. Made from reaction between carboxylic acid and amine and contain a number of secondary amide groups
28
Q

How do you name primary amides?

A
  • suffix: amide
  • root is generated from number of C atoms in hydrocarbon chain
    e. g. methanamide, ethanamide, propanamide
29
Q

How do you name secondary amides?

A
  • suffix: amide
  • root is generated by the number of C atoms in parent hydrocarbon chain which has the functional group
  • alkyl chain is attached to nitrogen, so its called an N-substituted compound
30
Q

What are optical isomers?

A

Molecules which are non superimposable mirror images (‘enantiomers’) of each other. They have the same chemical properties but interact with polarised light differently. Similar physical properties. May have different biological properties

31
Q

What is a chiral carbon?

A

Has 4 different groups attached to it

32
Q

How are optical isomers (enantiomers) named?

A

Given a prefix to denote its effect on a plane of polarised light:

  • ’+’ prefix if enantiomer rotates plane of polarised light in the clockwise direction
  • ’-‘ prefix if enantiomer rotates plane of polarised light in the anti-clockwise direction

(can only be deduced from equipment not their strucutre)

33
Q

What is a racemic mixture/racemate?

A

50:50 mixture of each enantiomer. Has no effect on polarised light as rotations of the 2 isomers cancel each other out

34
Q

What structural features must a compound have in order to display optical isomerism?

A
  • must be a carbon with 4 different groups attached: a chiral centre (often shows with a ‘*’)
  • inorganic atoms e.g. nitrogen can be chiral centres too
  • chiral molecules do not have a plane of symmetry due to the assymetric, or chiral, carbon. Some molecules have more than one chiral centre. Each will be a carbon atom with 4 different groups attached
35
Q

What is a repeat unit?

A

The arrangement of atoms that occurs many times in a polymer

36
Q

What is condensation polymerisation?

A

The chemical reaction to form a long chain molecule by elimination of a small molecule, e.g. water

37
Q

What are the differences between addition polymerisation and condensation polymerisation?

A
  • a: one monomer, c: 2 monomers
  • a: C=C that breaks open, c: different functional groups react together to form a polymer
  • c: small molecule released (often water), a: polymer is the only product
38
Q

How do you identify the type of polymer (addition or condensation) from their monomers?

A
  • addition: have at least one C=C double bond
  • condensation: each monomer has 2 different functional groups or more than one monomer present each with different functional groups
39
Q

How does a polyester form?

A

-dicarboxylic acid and diol

  • carboxylic acid group on one monomer reacts w alcohol group on other monomer
  • an ester link is formed between the 2 molecules
  • happens many times to produce a polyester

-monomer with carboxylic acid and alcohol groups

40
Q

How does a polyamide form?

A

-dicarboxylic acid and diamine

  • carboxylic acid from one monomer reacts w amine group on another monomer
  • forms an amide link
  • happens between many molecules forming a long chain polyamide

-amino acids can undergo condensation polymerisation to form a polyamide

Chemistry Year 12/13 (18 decks)

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