NUCLEOPHILIC SUBSTITUTION Flashcards

HALOGENOALKANES

1
Q

What are the bond polarities of the halogenoalkanes? (2)

A

halogenoalkanes have a C-X bond, the bond is polar because halogens are more electronegative than carbon. going down the group the atom gets less electronegative.

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2
Q

what are the trends in solubility in the halogenoalkanes? (3)

A

the polar C-X bonds are not polar enough to make them soluble in water.
the main intermolecular forces are dipole-dipole and van der waals
halogen alkanes mix with hydrocarbons so can be used in dry cleaning.

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3
Q

what are the trends in boiling point in the halogenoalkanes? (3)

A

-boiling point increases with increased chain length
-boiling point increases going down the halogen group
-which is caused by increase in van der waals forces.

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4
Q

what are the most electronegative halogenoalkanes? (4)

A

-fluorine -most
-chlorine
-bromine
-iodine -least

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5
Q

what are the prefixes for each of the halogenoalkanes? (4)

A

-fluoro
-chloro
-bromo
-iodo

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6
Q

what is a primary amine? (1)

A

a primary amine has one alkyl group on the nitrogen atom.

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7
Q

what is a tertiary amine? (1)

A

a tertiary amine has three alkyl groups on the nitrogen atom.

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8
Q

what is a secondary amine? (1)

A

a secondary amine has two alkyl groups on the nitrogen atom.

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9
Q

what is the formula for a carboxylic atom? (1)

A

COOH

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10
Q

What is the formula for an alcohol? (1)

A

RCH2OH

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11
Q

what can halogenoalkanes be converted to? (3)

A

-alcohols
-amines
-nitriles

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12
Q

what are the other functional groups of alcohols? (2)

A

-carboxylic acid
-aldehyde

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13
Q

what are the other functional groups of primary amines? (2)

A

-secondary amines
-tertiary amines

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14
Q

what are the other functional groups of nitriles? (2)

A

-carboxylic acid
-primary amine

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15
Q

why are nucleophilic substitutions useful? (1)

A

they introduce new functional groups into organic compounds.

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16
Q

what is the nucleophile when halogenoalkanes react with cyanide ions? (1)

A

the cyanide ion.

17
Q

what is the nucleophile when halogenoalkanes react with ammonia? (1)

A

the ammonium

18
Q

what do curly arrows represent? (1)

A

are used to show how electron pairs move in organic reactions.

19
Q

what is the leaving group? (1)

A

when the electron pair in the C-X bond moves to the halogen atom, X, making it a halide ion (the leaving group)

20
Q

what are produced from the mechanism with halogenoalkanes and cyanide ions? (1)

A

nitriles are formed.

21
Q

what is the overall reaction for halogenoalkanes with aqueous sodium (or potassium) hydroxide? (2)

A

R-X + OH(-) -> ROH + X(-)
Alcohol is formed

22
Q

what is the nucleophile for halogenoalkanes with aqueous sodium (or potassium) hydroxide? (1)

A

the nucleophile is the hydroxide ion (OH-)

23
Q

what is a nucleophile? (1)

A

reagents that attack and form bonds with positively or partially positively charged carbon atoms.

24
Q

what is classified as a nucleophile? (1)

A

a nucleophile is either a negatively charged ion or has an atom with a partial negative charge.

25
what does the rate of substitution depend on? (1)
depends on the halogen; going down the group bond strength increases.
26
what are nucleophile substitution reactions? (1)
nucleophiles that replace the halogen in a halogenoalkane.
27
what are the most common nucleophiles? (3)
-the hydroxide ion (OH) -ammonia (NH3) -the cyanide ion (CN-)
28
what are the physical properties of the halogenoalkanes? (3)
solubility -boiling point -melting point
29
how reactive are the halogenoalkanes? (2)
how reactive the halogenoalkanes are depends on how reactive the C-X bond is, they are effected by two factors; -the C-X bond polarity -the C-X bond enthalpy
30
what are some properties of nucleophiles? (2)
-a nucleophile has a lone (unshared) pair of electrons which it can use to form a covalent bond. -the lone pair is situated on an electronegative atom
31
how does bond polarity effect the reactivity of the halogenoalkanes? (2)
the carbon bonded to the halogen has a partial positive charge - its electron deficient - this mean that it can be attacked by reagents that are electron rich (nucleophiles). the C-F bond is most polar so is the most reactive.
32
how does the bond enthalpy effect the reactivity of the halogenoalkanes? (2)
the bond gets weaker going down the group. C-F is the stronger bond as it is a smaller atom, going down the group atoms get bigger minimising the attraction between the protons in the nucleus and the electrons in the outer electron shells.
33
what is a reaction mechanism? (1)
describe a route from reactants to products via a series of theoretical steps which may involve short lived intermediates.