Chemistry U4: Textbook > 4.6 > Flashcards

4.6 Flashcards

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1
Q

What is the defining feature of all amines?

A

All amines contain a nitrogen atom bonded directly to a carbon atom of an alkyl or aryl group.

Alkyl groups are derived from alkanes by removing one hydrogen atom, while aryl groups are derived from aromatic compounds.

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2
Q

What is a primary amine?

A

A primary amine has the nitrogen atom bonded directly to only one carbon atom.

Example: butylamine.

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3
Q

How is a secondary amine defined?

A

A secondary amine has the nitrogen atom bonded directly to two carbon atoms.

Example: 1-methylpropylamine.

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4
Q

What characterizes a tertiary amine?

A

A tertiary amine has the nitrogen atom bonded directly to three carbon atoms.

Example: triethylamine.

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5
Q

What suffix is used in the naming of amines?

A

-amine

This suffix is added to the longest carbon chain identified in the amine.

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6
Q

What is an aromatic amine?

A

An aromatic amine has the nitrogen atom of the -NH2 group bonded directly to a benzene ring.

Example: phenylamine.

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7
Q

Fill in the blank: The longest carbon chain is used to name the amine, with the number of carbon atoms indicated in the usual way and _______ used as the suffix.

A

-amine.

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8
Q

What is trietylamine?

A

Triethylamine is a tertiary amine.

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9
Q

How are primary aliphatic amines formed from halogenoalkanes?

A

By reacting a halogenoalkane with ammonia in a water/ethanol solvent.

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10
Q

What happens if the mixture of halogenoalkane and ammonia is warmed?

A

Ammonia gas is lost from the mixture, reducing the yield.

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11
Q

What method can increase the yield of primary aliphatic amines?

A

Using the reactants in a sealed tube and gently heating.

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12
Q

Why is an excess of ammonia generally used in the reaction?

A

To react with the acidic gas hydrogen bromide, forming ammonium bromide.

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13
Q

Fill in the blank: The reaction of a halogenoalkane with ammonia produces an _______.

A

amine

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14
Q

True or False: Heating the mixture of halogenoalkane and ammonia always increases the yield of amines.

A

False

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15
Q

What type of mechanism is used for the formation of the amine?

A

Nucleophilic substitution

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16
Q

What is the usual product formed from the amine under certain conditions?

A

Its salt

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17
Q

What is propylammonium bromide?

A

A substituted ammonium bromide (NH4Br) with one hydrogen atom replaced by a propyl group

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18
Q

What is produced when an ammonium salt is heated with a base?

A

Ammonia

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19
Q

What do you obtain when propylammonium bromide is heated with aqueous sodium hydroxide?

A

Propylamine

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20
Q

How can primary aliphatic amines be made from nitriles?

A

By reducing nitriles with a suitable reducing agent

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21
Q

What is the usual reducing agent for nitriles?

A

Lithium tetrahydridoaluminate(III) [H] in ethoxyethane

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22
Q

This reaction has been discussed in the section on _______.

A

Carboxylic acids

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23
Q

What is the primary challenge in the reaction of benzene with nucleophiles?

A

Benzene is not easily attacked by nucleophiles due to ring electrons repelling nucleophiles and attracting electrophiles.

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24
Q

What is the traditional reducing agent used for the reduction of nitrobenzene?

A

Tin metal and hydrochloric acid

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25
What are more economical reducing agents for making phenylamine commercially?
* Hydrogen and a nickel catalyst * Iron and hydrochloric acid
26
Fill in the blank: Phenylamine is produced by the reduction of _______.
nitrobenzene
27
True or False: Derivatives of nitrobenzene can be reduced in a similar way to nitrobenzene.
True
28
What is the basic structure of amines?
Amines have a lone pair of electrons on the nitrogen atom.
29
How do amines demonstrate their basic nature in reactions with water?
Smaller amines react with water to form hydroxide ions and methylammonium ions.
30
Why are alkylamines stronger bases than ammonia?
Alkyl groups push electrons towards the nitrogen atom.
31
What makes phenylamine a much weaker base compared to ammonia or alkylamines?
The nitrogen lone pair becomes part of the delocalised π system.
32
What effect does the nitrogen lone pair have on phenylamine's reactivity?
It makes phenylamine more susceptible to electrophilic ring substitution.
33
Why is phenylamine only slightly soluble in water?
Due to the hydrophobic effect of the benzene ring.
34
What happens when amines react with acids?
They form salts.
35
Fill in the blank: Methylamine is a _______ base.
weak
36
True or False: Phenylamine has a strong fishy smell.
False
37
What is the product formed when phenylamine reacts with hydrochloric acid?
Phenylammonium chloride.
38
What role do amines play in chemical reactions?
Amines react as nucleophiles due to the nitrogen lone pair
39
What do amines attack in an acid chloride reaction?
The + carbon atom of the carbonyl group
40
What does the letter 'N' signify in N-methylethanamide?
The methyl group is bonded to the nitrogen atom
41
What is N-methylethanamide an example of?
An N-substituted derivative of ethanamide
42
What is the general structure of a peptide linkage?
- N - C -
43
Where else is the peptide linkage found?
In peptides, polypeptides, and proteins
44
What type of polymers contain the peptide linkage?
Polyamides such as nylon
45
What is a familiar compound that contains the peptide linkage?
Paracetamol
46
Fill in the blank: The organic product of the reaction between an amine and an acid chloride is called _______.
N-methylethanamide
47
What is the chemical formula for nitrous acid?
HNO2
48
How is nitrous acid prepared?
By the reaction of a dilute acid (e.g., HCl) on sodium nitrate(I) (NaNO2) ## Footnote NaNO2 + HCl → HNO2 + NaCl
49
What gas is evolved when a primary aliphatic amine reacts with nitric (III) acid?
Nitrogen gas (N2)
50
What is the yield of the alcohol in the reaction of primary amines with nitric (III) acid?
Poor
51
What is formed initially when a primary aliphatic amine reacts with nitric (III) acid?
An alkyl diazonium ion (R—N+=N)
52
What type of amine reacts with nitric (III) acid to produce a more stable diazonium intermediate?
Primary aromatic amine
53
What is the name of the diazonium ion produced from phenylamine?
Benzenediazonium ion
54
What is produced when the reaction temperature is between 0°C and 10°C?
A solution containing benzenediazonium ion
55
What happens to the benzenediazonium compound above 10°C?
Decomposition occurs, giving phenol
56
True or False: The production of the benzenediazonium compound is too slow if the reaction temperature is below 0°C.
True
57
What are benzenediazonium compounds used for?
Intermediates in the formation of many other compounds
58
What happens to nitrogen atoms during the formation of phenol from benzenediazonium chloride?
They are lost as nitrogen gas
59
At what temperature do benzenediazonium compounds react with phenols and aromatic amines?
Below 10°C
60
What group is retained in the compounds formed from the reaction of benzenediazonium with phenols and aromatic amines?
-N=N- azo group
61
What type of electrophile is the benzenediazonium ion?
Weak electrophile
62
How does the benzenediazonium ion bond with aromatic compounds?
Via electrophilic substitution
63
What activates the aromatic compounds for the reaction with benzenediazonium ion?
Presence of -OH or -NH2 groups
64
What are the characteristics of the resulting compound from the coupling reaction with benzenediazonium?
Highly coloured, generally yellow, orange or red
65
What is the common name for the resulting compound from the coupling reaction?
Azo dye
66
In what type of solution is the coupling reaction often carried out?
Alkaline solution
67
At which position does coupling often occur relative to the -OH or -NH2 group?
4-position
68
True or False: Coupling can only occur at the 4-position relative to the -OH or -NH2 group.
False
69
Fill in the blank: Benzenediazonium ions react with phenols and aromatic amines to produce azo compounds in _______ conditions.
alkaline
70
What is the structure represented by N=N in the context of azo compounds?
Azo group ## Footnote The azo group is a functional group that contains a nitrogen-nitrogen double bond.
71
What is the product formed when (4-phenylazo)phenol reacts with sodium hydroxide?
(1-phenylazo)naphthalen-2-ol ## Footnote This compound is formed through a coupling reaction involving aromatic systems.
72
What type of chemical reaction occurs between (4-phenylazo)phenol and naphthalen-2-ol?
Coupling reaction ## Footnote Coupling reactions involve the formation of a bond between two aromatic compounds.
73
What is the name of the azo dye formed from naphthalen-2-ol?
Sudan 1 ## Footnote Sudan 1 is a red solid azo dye that has been used to color food products like curry powder.
74
True or False: The use of Sudan 1 to color curry powder is still allowed in the United Kingdom.
False ## Footnote The use of Sudan 1 for coloring food products has been banned in the UK.
75
What are the byproducts of the reaction involving (4-phenylazo)phenol, NaOH, and NaCl?
NaCl and H2O ## Footnote These byproducts are generated during the coupling reaction in the presence of sodium hydroxide.
76
Fill in the blank: Coupling can also occur with other _______ systems.
aromatic ## Footnote Aromatic systems are characterized by their stable ring structures and delocalized electrons.
77
What is a chromophore?
A structural unit in a molecule responsible for the absorption of radiation of a certain wavelength.
78
What happens to the color observed in relation to the light absorbed by a chromophore?
The color observed is the color that is not absorbed.
79
What factors influence the actual wavelengths of light absorbed by a chromophore?
Other groups present in the molecule.
80
What is the absorption maximum wavelength for the -N=N- chromophore associated with yellow?
384 nm.
81
What is the absorption maximum wavelength for the -N=N- chromophore associated with orange red?
476 nm.
82
What is the absorption maximum wavelength for the -N=N- chromophore associated with red?
520 nm.
83
What is the relationship between the intensity of color observed in solution and the concentration of the compound?
The intensity of the color depends on the concentration of the compound present.
84
What is the basis of colorimetry?
The relationship between the intensity of color observed and the concentration of the compound present.
85
What does the color hexagon indicate?
It indicates the color absorbed and the color transmitted (not absorbed) when light is shone through the sample.
86
Fill in the blank: The absorption maximum wavelength for -N=N- associated with yellow is _______.
384 nm
87
True or False: The color that is observed is the color that is absorbed by the chromophore.
False.
88
What is the colour of a solution of Sudan 1?
Red ## Footnote Sudan 1 has a maximum absorption in the blue-green region.
89
What is the opposite colour to red in the colour hexagon?
Blue-green ## Footnote This indicates the absorption characteristics of Sudan 1.
90
At what wavelength does Sudan 1 have its maximum absorption?
476 nm ## Footnote This wavelength is in the blue-green region.
91
What is the maximum absorption wavelength of methylene blue?
668 nm ## Footnote This wavelength falls in the red region of the spectrum.
92
What colour does methylene blue appear to be?
Bluish ## Footnote The bluish colour is opposite red in the colour hexagon.
93
Fill in the blank: The maximum absorption of methylene blue is at _______.
668 nm
94
True or False: Sudan 1's maximum absorption occurs in the red region of the spectrum.
False ## Footnote Sudan 1's maximum absorption occurs in the blue-green region.
95
True or False: The visible spectrum of methylene blue shows absorption at 476 nm.
False ## Footnote The maximum absorption of methylene blue is at 668 nm.
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