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Chemistry > Chapter 6: Haloalkanes and Haloarenes > Flashcards

Chapter 6: Haloalkanes and Haloarenes Flashcards

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1
Q

What are the classifications of haloalkanes and haloarenes based on the number of halogen atoms?

A

They can be classified as mono, di, or polyhalogen compounds.

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2
Q

What is the general formula for alkyl halides?

A

CnH2n+1X

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3
Q

How are alkyl halides classified based on the carbon atom they are attached to?

A

They are classified as primary (1°), secondary (2°), or tertiary (3°) alkyl halides.

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4
Q

What defines allylic halides?

A

Halogen is bonded to an sp3-hybridised carbon atom adjacent to a carbon-carbon double bond.

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5
Q

What defines benzylic halides?

A

Halogen is bonded to an sp3-hybridised carbon atom attached to an aromatic ring.

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6
Q

What are vinylic halides?

A

Compounds where the halogen atom is bonded to an sp2-hybridised carbon atom of a carbon-carbon double bond.

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7
Q

What are aryl halides?

A

Compounds where the halogen atom is directly bonded to the sp2-hybridised carbon atom of an aromatic ring.

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8
Q

In the common naming system, how are mono halogen substituted derivatives of benzene named?

A

They are named the same in both common and IUPAC systems.

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9
Q

What prefixes are used in the common naming system for dihalogen derivatives?

A

o-, m-, p-

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10
Q

How are geminal halides defined?

A

Both halogen atoms are present on the same carbon atom.

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11
Q

What are vicinal halides?

A

Halogen atoms are present on adjacent carbon atoms.

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12
Q

What is the bond character of carbon-halogen bonds in alkyl halides?

A

They are polarised, with carbon bearing a partial positive charge and halogen bearing a partial negative charge.

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13
Q

Which halogen has the smallest atom size?

A

Fluorine

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14
Q

What method is preferred for preparing alkyl halides from alcohols?

A

Thionyl chloride is preferred because it produces gases that escape.

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15
Q

What is the order of reactivity of alcohols with haloacids?

A

3° > 2° > 1°

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16
Q

What is Finkelstein reaction?

A

The reaction of alkyl chlorides/bromides with NaI in dry acetone to form alkyl iodides.

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17
Q

What is Swarts reaction?

A

Heating an alkyl chloride/bromide in the presence of a metallic fluoride to synthesize alkyl fluorides.

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18
Q

What type of reaction is used to prepare aryl halides?

A

Electrophilic substitution of arenes with chlorine or bromine.

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19
Q

What is formed when a primary aromatic amine is treated with sodium nitrite?

A

A diazonium salt.

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20
Q

What is the general trend for the carbon-halogen bond lengths?

A

Bond length increases from C—F to C—I.

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21
Q

What is the significance of Markovnikov’s rule in alkene reactions?

A

It predicts the predominance of one product over others during the addition of hydrogen halides.

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22
Q

What is the main characteristic of nucleophilic substitution reactions involving haloalkanes?

A

A nucleophile reacts with haloalkane, causing the halogen atom to depart as a halide ion.

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23
Q

What are some common nucleophiles used in nucleophilic substitution reactions?

A
  • NaOH (KOH) * NaI * NH3 * Alcohols
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24
Q

What happens during the free radical monochlorination of (CH3)2CHCH2CH3?

A

Four different types of hydrogen atoms are replaced, resulting in multiple structural isomers.

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25
What is the general formula for Alkyl Halides?
R–X
26
What are the nucleophiles involved in the reaction with NaOH?
HO–
27
What is the product formed when alcohol reacts with water?
ROH
28
What is the product of the reaction between NaI and an alkyl group?
Alkyl iodide (R—I)
29
What type of amine is produced when a primary amine reacts with NH3?
Primary amine (RNH2)
30
What is the structure of a secondary amine?
RNHR'
31
What is the structure of a tertiary amine?
RNR'R''
32
What is the product when KCN reacts with an alkyl group?
Nitrile (RCN)
33
What is produced when AgCN reacts with an alkyl group?
Isonitrile (RNC)
34
What is the product formed from KNO2?
Alkyl nitrite (R—O—N=O)
35
What is the general product when AgNO2 reacts with an alkyl group?
Nitroalkane (R—NO2)
36
What is the product formed when an alkyl group reacts with LiAlH4?
Hydrocarbon (RH)
37
What is the reactivity order of alkyl halides in SN2 reactions?
Primary halide > Secondary halide > Tertiary halide
38
What is the mechanism of SN1 reaction?
Occurs in two steps: 1. Carbocation formation 2. Nucleophile attack
39
What type of solvent is generally used for SN1 reactions?
Polar protic solvents (like water, alcohol, acetic acid)
40
What is the effect of bulky substituents on SN2 reactions?
They inhibit the reaction by hindering nucleophile approach
41
What happens to the configuration during an SN2 reaction?
Inversion of configuration
42
What is the definition of 'configuration' in chemistry?
Spatial arrangement of functional groups around carbon
43
What are optical isomers?
Compounds that rotate plane polarized light differently
44
What is chirality?
Property of a molecule that is non-superimposable on its mirror image
45
What is retention of configuration?
Preservation of spatial arrangement during a reaction
46
What occurs during racemisation?
Formation of a 50:50 mixture of two optical isomers
47
What is the result of SN2 reactions of optically active halides?
Inversion of configuration
48
What is the result of SN1 reactions of optically active halides?
Racemisation
49
What is the configuration change in SN2 reactions compared to the reactant?
Inversion of configuration ## Footnote This occurs because the nucleophile attaches on the side opposite to the halogen atom.
50
What product is formed when (–)-2-bromooctane reacts with sodium hydroxide?
(+)-octan-2-ol ## Footnote The –OH group occupies the position opposite to the bromide.
51
What happens to optically active alkyl halides in SN1 reactions?
Racemisation ## Footnote This occurs because the carbocation formed is planar and can be attacked from either side.
52
What is the α-carbon in a molecule?
The carbon on which the halogen atom is directly attached ## Footnote The adjacent carbon is referred to as the β-carbon.
53
What is the result of heating a haloalkane with an alcoholic solution of potassium hydroxide?
Formation of an alkene ## Footnote This is an elimination reaction where a hydrogen atom from the β-carbon and a halogen atom from the α-carbon are eliminated.
54
What is Zaitsev's rule?
In dehydrohalogenation reactions, the preferred product is the alkene with the greater number of alkyl groups attached to the doubly bonded carbon atoms ## Footnote This rule explains why 2-bromopentane gives pent-2-ene as the major product.
55
What factors determine whether substitution or elimination will occur in a reaction?
Nature of alkyl halide, strength and size of base/nucleophile, and reaction conditions ## Footnote A bulkier nucleophile tends to act as a base, while a primary alkyl halide prefers SN2.
56
What are Grignard reagents?
Alkyl magnesium halides, RMgX ## Footnote These are formed by the reaction of haloalkanes with magnesium metal in dry ether.
57
What is the significance of avoiding moisture in reactions with Grignard reagents?
Grignard reagents react with any source of proton, including moisture ## Footnote This is why these reactions are conducted in dry ether.
58
What is the Wurtz reaction?
Alkyl halides react with sodium in dry ether to give hydrocarbons with double the number of carbon atoms present in the halide ## Footnote This reaction is useful for creating larger alkanes.
59
Why are aryl halides less reactive towards nucleophilic substitution?
Due to resonance effects and the sp2 hybridization of the carbon atom attached to halogen ## Footnote The C—Cl bond in haloarene has partial double bond character, making it harder to cleave.
60
How does the presence of an electron withdrawing group affect the reactivity of haloarenes?
Increases reactivity when positioned at ortho- and para- positions ## Footnote This is due to the facilitation of nucleophilic attack and stabilization of the carbanion formed.
61
What is the effect of chlorine in electrophilic aromatic substitution reactions?
Ortho- and para- directing despite being electron withdrawing ## Footnote Chlorine destabilizes the carbocation through inductive effect but stabilizes it through resonance.
62
What is the main use of dichloromethane?
Solvent for paint, propellant in aerosols, and process solvent in drug manufacture ## Footnote It is also used for metal cleaning and finishing.
63
What are some health effects of exposure to chloroform?
Dizziness, fatigue, headache, liver damage ## Footnote Chloroform was once used as an anesthetic but is now known to have significant health risks.
64
What are freons?
Stable, non-toxic gases used in refrigeration and aerosol propellants ## Footnote They are derived from chlorofluorocarbons and contribute to ozone depletion.
65
What is DDT and its significance?
The first chlorinated organic insecticide, effective from 1939 ## Footnote Paul Muller received the Nobel Prize for its discovery due to its effectiveness as an insecticide.
66
What is the annual production of freon?
2 billion pounds annually
67
Where does most freon eventually end up?
In the atmosphere, diffusing unchanged into the stratosphere
68
What effect does freon have in the stratosphere?
It can initiate radical chain reactions that upset the natural ozone balance
69
Who discovered the effectiveness of DDT as an insecticide?
Paul Muller of Geigy Pharmaceuticals in Switzerland
70
In what year was DDT first prepared?
1873
71
When did Paul Muller win the Nobel Prize for his discovery of DDT?
1948
72
What was a major reason for the worldwide increase in DDT use after World War II?
Its effectiveness against the mosquito that spreads malaria and lice that carry typhus
73
What problems arose from the extensive use of DDT?
* Insect resistance to DDT * High toxicity towards fish * Chemical stability and fat solubility
74
How is DDT metabolized in animals?
It is not metabolized rapidly; it is deposited and stored in fatty tissues
75
When was the use of DDT banned in the United States?
1973
76
What classification can alkyl/aryl halides have based on the number of halogen atoms?
Mono, di, or polyhalogen (tri-, tetra-, etc.)
77
What charge does the carbon atom bear in a carbon-halogen bond of alkyl halides?
Partial positive charge
78
What charge does the halogen atom bear in a carbon-halogen bond of alkyl halides?
Partial negative charge
79
How are alkyl halides prepared?
* Free radical halogenation of alkanes * Addition of halogen acids to alkenes * Replacement of -OH group of alcohols with halogens
80
Which compound will react faster in an SN2 reaction with -OH: CH3Br or CH3Cl?
CH3Br
81
What type of reaction is dehydrohalogenation?
A reaction to form alkenes from halides
82
What is the major alkene formed from 1-Bromo-1-methylcyclohexane?
Cyclohexene
83
What is the method to convert ethanol to but-1-yne?
Dehydration followed by an elimination reaction
84
Why do alkyl halides, though polar, remain immiscible with water?
Due to their hydrophobic nature
85
What is the structure of the major organic product formed when CH3CH2Br reacts with NaI in acetone?
CH3CH2I
86
What happens when n-butyl chloride is treated with alcoholic KOH?
Formation of alkenes
87
What is the outcome of treating bromobenzene with Mg in dry ether?
Formation of a Grignard reagent
88
What is the product of the hydrolysis of chlorobenzene?
Phenol
89
What is the product when methyl bromide is treated with sodium in dry ether?
n-Butane
90
What is the major product of the reaction of 1-Bromopropane to 2-bromopropane?
2-Bromopropane
91
What is the reason for lower dipole moment in chlorobenzene compared to cyclohexyl chloride?
Resonance stabilization in chlorobenzene
92
What is the product of treating ethyl chloride with aqueous KOH?
Ethanol
93
What is the product of treating isopropyl alcohol with iodoform?
Iodoform
94
What happens to primary alkyl halides when treated with alcoholic KOH?
They undergo elimination to form alkenes
95
What is the structural formula of the compound that reacts with sodium to give C8H18?
2-Methyl-1-pentane
96
What is the major product of the reaction between (CH3)3CBr and KOH?
Isobutylene
97
What type of alkyl halide reacts fastest in SN2 reactions?
Primary alkyl halides
98
What is the effect of branching on the boiling point of alkyl halides?
Boiling point decreases with increased branching
99
What happens when 2-Bromopropane is treated with KCN?
Formation of propanenitrile
100
Fill in the blank: The treatment of alkyl chlorides with aqueous KOH leads to the formation of _______.
Alcohols
101
Fill in the blank: The reaction of 1-Bromopropane with alcoholic KOH gives compound (b), which is then reacted with HBr to give compound (c), an isomer of _______.
1-Bromopropane

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