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Topic 6.3 (Halogenoalkanes) > Halogenoalkanes and hydrolysis reactions > Flashcards

Halogenoalkanes and hydrolysis reactions Flashcards

1
Q

define nucleophile

A

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

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2
Q

what is a hydrolysis reaction?

A

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

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3
Q

what is the general formula of halogenoalkanes?

A

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

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4
Q

can you have different numbers of halogen atoms in halogenoalkanes?

A

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

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5
Q

why are halogenoalkanes reactive?

A

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.

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6
Q

why are hydrocarbons less reactive than halogenoalkanes?

A

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.

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7
Q

what is trend of electronegativity down group 7?

A

decreases from fluorine to iodine

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8
Q

what does ‘lysis’ mean?

A

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

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9
Q

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

A

RX

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10
Q

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

A

R2CHX

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11
Q

what does ‘nucleo’ mean?

A

positive charge

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12
Q

what does ‘phile’ mean?

A

liking

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13
Q

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

A

three and tertiary

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14
Q

what are nucleophiles attracted to?

A

slightly positive or electron deficient parts of molecules.

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15
Q

halogenoalkanes are

A

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

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16
Q

X represents

A

a halogen atom

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17
Q

R represents

A

an alkyl group

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18
Q

examples of alkyl groups are

A

methyl or ethyl

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19
Q

the simplified formula for halogenoalkanes is

A

RX

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20
Q

the simplified formula of halogenoalkanes is RX because

A

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

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21
Q

alkyl groups are

A

alkanes missing one hydrogen

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22
Q

the number of halogen atoms in a halogenoalkane can be

A

more than one

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23
Q

the general formula for halogenoalkanes containing two halogen atoms is

A

Cn H2n X2

24
Q

the general formula for halogenoalkanes containing three halogen atoms is

A

Cn H2n-1 X3

25
Q

the most notorious halogenoalkanes are

A

chlorofluorocarbons (CFCs for short)

26
Q

CFCs contain

A

both chlorine and fluorine

27
Q

CFCs were used in

A

aerosol cans

28
Q

CFCs can

A

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

29
Q

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

A

name the halogen prefixes in alphabetical order

30
Q

the prefix numbers should

A

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

31
Q

a primary halogenoalkanes means

A

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

32
Q

a secondary halogenoalkanes means

A

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

33
Q

a tertiary halogenoalkane means

A

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

34
Q

the halogenoalkanes CH3X is

A

primary

35
Q

hydrocarbons contain

A

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

36
Q

hydrogen and carbon atoms have

A

similar electronegativities

37
Q

bonds which contain atoms of similar electronegativities are

A

almost non-polar

38
Q

halogen atoms have a higher

A

electronegativity than carbon

39
Q

partial charge for polar bonds is shown by

A

δ+ and δ-

40
Q

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

A

decreases, because the electronegativity of halogens decreases down Group 7

41
Q

the carbon atom joined to the halogen is always

A

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

42
Q

halogens are reactive because of

A

the slightly positive carbon atom joined to the halogen

43
Q

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

A

nucleophiles

44
Q

nucleophiles are either

A

negative ions or molecules with a slightly negative atom

45
Q

nucleophiles always

A

use (donate) a pair of lone electrons when attacking

46
Q

nucleophiles form……. when attacking

A

a covalent bond with an electron deficient atom

47
Q

when a halogenoalkanes is added to water

A

a reaction begins

48
Q

the reaction between a halogenoalkane and water

A

may take a period of time to complete

49
Q

a water molecules contains

A

polar polar bonds

50
Q

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

A

δ- O and δ+ H

51
Q

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

A

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

52
Q

hydrolysis reaction with halogenoalkanes results in the production of

A

an alcohol

53
Q

the equations for the hydrolysis reaction with a halogenoalkane are

A

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

54
Q

the hydrolysis reaction with halogenoalkanes are difficult to observe as

A

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

55
Q

in the hydrolysis reaction with a halogenoalkane,

A

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

Topic 6.3 (Halogenoalkanes) (3 decks)

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