NUCLEOPHILIC SUBSTITUTION

Question 1

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

Answer 1

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.

Question 2

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

Answer 2

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.

Question 3

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

Answer 3

-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.

Question 4

what are the most electronegative halogenoalkanes? (4)

Answer 4

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

Question 5

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

Answer 5

-fluoro
-chloro
-bromo
-iodo

Question 6

what is a primary amine? (1)

Answer 6

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

Question 7

what is a tertiary amine? (1)

Answer 7

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

Question 8

what is a secondary amine? (1)

Answer 8

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

Question 9

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

Answer 9

COOH

Question 10

What is the formula for an alcohol? (1)

Answer 10

RCH2OH

Question 11

what can halogenoalkanes be converted to? (3)

Answer 11

-alcohols
-amines
-nitriles

Question 12

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

Answer 12

-carboxylic acid
-aldehyde

Question 13

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

Answer 13

-secondary amines
-tertiary amines

Question 14

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

Answer 14

-carboxylic acid
-primary amine

Question 15

why are nucleophilic substitutions useful? (1)

Answer 15

they introduce new functional groups into organic compounds.

Question 16

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

Answer 16

the cyanide ion.

Question 17

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

Answer 17

the ammonium

Question 18

what do curly arrows represent? (1)

Answer 18

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

Question 19

what is the leaving group? (1)

Answer 19

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

Question 20

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

Answer 20

nitriles are formed.

Question 21

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

Answer 21

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

Question 22

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

Answer 22

the nucleophile is the hydroxide ion (OH-)

Question 23

what is a nucleophile? (1)

Answer 23

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

Question 24

what is classified as a nucleophile? (1)

Answer 24

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

Question 25

what does the rate of substitution depend on? (1)

Answer 25

depends on the halogen; going down the group bond strength increases.

Question 26

what are nucleophile substitution reactions? (1)

Answer 26

nucleophiles that replace the halogen in a halogenoalkane.

Question 27

what are the most common nucleophiles? (3)

Answer 27

-the hydroxide ion (OH)
-ammonia (NH3)
-the cyanide ion (CN-)

Question 28

what are the physical properties of the halogenoalkanes? (3)

Answer 28

solubility
-boiling point
-melting point

Question 29

how reactive are the halogenoalkanes? (2)

Answer 29

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

Question 30

what are some properties of nucleophiles? (2)

Answer 30

-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

Question 31

how does bond polarity effect the reactivity of the halogenoalkanes? (2)

Answer 31

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.

Question 32

how does the bond enthalpy effect the reactivity of the halogenoalkanes? (2)

Answer 32

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.

Question 33

what is a reaction mechanism? (1)

Answer 33

describe a route from reactants to products via a series of theoretical steps which may involve short lived intermediates.