Halogenoalkanes and hydrolysis reactions

Question 1

define nucleophile

Answer 1

a species that donates a lone pair of electrons to form a covalent bond with an electron-deficient atom

Question 2

what is a hydrolysis reaction?

Answer 2

a reaction in which water or hydroxide ions (OH-) replace an atom in a molecule with an OH group

Question 3

what is the general formula of halogenoalkanes?

Answer 3

CnH2n+1X where X is a halogen atom. the equation can be simplified to RX where R is an alkyl group

Question 4

can you have different numbers of halogen atoms in halogenoalkanes?

Answer 4

yes, and this is represented by a number preceding the X in the general formula, for example, 1,2 dichloropropane would be part of the series abiding by the general formula CnH2n+1X2

Question 5

why are halogenoalkanes reactive?

Answer 5

because they have a halogen to carbon bond which is polar as the halogen has a higher electronegativity than carbon. The carbon atom joined to the halogen is always slightly positive, or electron-deficient, so this is what makes halogenoalkanes react as they do.

Question 6

why are hydrocarbons less reactive than halogenoalkanes?

Answer 6

hydrocarbons contain hydrogen and carbon atoms only, which have similar electronegativities, their bonds are almost non-polar, while halogenoalkanes contain a halogen carbon bond where the halogen has a higher electronegativity than carbon, so the C-X bond is polar.

Question 7

what is trend of electronegativity down group 7?

Answer 7

decreases from fluorine to iodine

Question 8

what does ‘lysis’ mean?

Answer 8

refers to splitting, like splitting water in hydrolysis and splitting compounds in electrolysis

Question 9

what is the abbreviated formula of CH3-CH2-CH2F ?

Answer 9

RX

Question 10

what is the abbreviated formula of CH3-CHBr-CH3 ?

Answer 10

R2CHX

Question 11

what does ‘nucleo’ mean?

Answer 11

positive charge

Question 12

what does ‘phile’ mean?

Answer 12

liking

Question 13

how many alkyl groups are in this compound, (CH3)2 CCl-CH2-CH3 ? and what classification is it? (primary, secondary etc…)

Answer 13

three and tertiary

Question 14

what are nucleophiles attracted to?

Answer 14

slightly positive or electron deficient parts of molecules.

Question 15

halogenoalkanes are

Answer 15

a homologous series of compounds with the general formula CnH2n+1 X

Question 16

X represents

Answer 16

a halogen atom

Question 17

R represents

Answer 17

an alkyl group

Question 18

examples of alkyl groups are

Answer 18

methyl or ethyl

Question 19

the simplified formula for halogenoalkanes is

Answer 19

RX

Question 20

the simplified formula of halogenoalkanes is RX because

Answer 20

R represents any alkyl group and X represents the halogen atom present in the compound

Question 21

alkyl groups are

Answer 21

alkanes missing one hydrogen

Question 22

the number of halogen atoms in a halogenoalkane can be

Answer 22

more than one

Question 23

the general formula for halogenoalkanes containing two halogen atoms is

Answer 23

Cn H2n X2

Question 24

the general formula for halogenoalkanes containing three halogen atoms is

Answer 24

Cn H2n-1 X3

Question 25

the most notorious halogenoalkanes are

Answer 25

chlorofluorocarbons (CFCs for short)

Question 26

CFCs contain

Answer 26

both chlorine and fluorine

Question 27

CFCs were used in

Answer 27

aerosol cans

Question 28

CFCs can

Answer 28

damage the ozone layer in the atmosphere, so have been phased out

Question 29

when naming halogenoalkanes with more than one type of halogen atom,

Answer 29

name the halogen prefixes in alphabetical order

Question 30

the prefix numbers should

Answer 30

be as small as possible when added together, and their sum cannot exceed the length of the longest carbon chain used in the naming

Question 31

a primary halogenoalkanes means

Answer 31

the carbon atom to which the halogen atom is bonded is itself bonded to only one other carbon atom

Question 32

a secondary halogenoalkanes means

Answer 32

the carbon atom to which the halogen atom is bonded to is itself bonded to two other carbon atoms

Question 33

a tertiary halogenoalkane means

Answer 33

the carbon atom to which the halogen atom is bonded to is itself bonded to three other carbon atoms

Question 34

the halogenoalkanes CH3X is

Answer 34

primary

Question 35

hydrocarbons contain

Answer 35

only hydrogen and carbon atoms, which have similar electronegativities, so their bonds are almost non-polar

Question 36

hydrogen and carbon atoms have

Answer 36

similar electronegativities

Question 37

bonds which contain atoms of similar electronegativities are

Answer 37

almost non-polar

Question 38

halogen atoms have a higher

Answer 38

electronegativity than carbon

Question 39

partial charge for polar bonds is shown by

Answer 39

δ+ and δ-

Question 40

the polarity of the C-X bond ........... as halogens from further down Group 7 are present

Answer 40

decreases, because the electronegativity of halogens decreases down Group 7

Question 41

the carbon atom joined to the halogen is always

Answer 41

slightly positive, δ+ or electron deficient part of the molecule

Question 42

halogens are reactive because of

Answer 42

the slightly positive carbon atom joined to the halogen

Question 43

δ+ carbon atoms or electron deficient carbon atoms attract species called

Answer 43

nucleophiles

Question 44

nucleophiles are either

Answer 44

negative ions or molecules with a slightly negative atom

Question 45

nucleophiles always

Answer 45

use (donate) a pair of lone electrons when attacking

Question 46

nucleophiles form....... when attacking

Answer 46

a covalent bond with an electron deficient atom

Question 47

when a halogenoalkanes is added to water

Answer 47

a reaction begins

Question 48

the reaction between a halogenoalkane and water

Answer 48

may take a period of time to complete

Question 49

a water molecules contains

Answer 49

polar polar bonds

Question 50

in a water molecule, the oxygen atom is and the hydrogen atoms are

Answer 50

δ- O and δ+ H

Question 51

in a hydrolysis reaction with a halogenoalkanes, the δ- oxygen atom in the water is attracted to

Answer 51

δ- oxygen atom in the water is attracted to the δ+ carbon atom in the halogenoalkane

Question 52

hydrolysis reaction with halogenoalkanes results in the production of

Answer 52

an alcohol

Question 53

the equations for the hydrolysis reaction with a halogenoalkane are

Answer 53

RX + H2O = ROH + HX or RX + H2O = ROH + H+ + X-

Question 54

the hydrolysis reaction with halogenoalkanes are difficult to observe as

Answer 54

both organic substances, halogenoalkane and alcohol, are colourless, so no colour change can be seen

Question 55

in the hydrolysis reaction with a halogenoalkane,

Answer 55

the C-X bond breaks, so the RX molecule break into two parts, the R(alkyl group) and the X (halogen atom). The R group then combines with the OH group of water