Qualitative Test for Hydrocarbons Flashcards

1
Q

Hydrocarbons – can be grouped into four structural classes

A

Alkane
Alkene
Alkyne
Aromatic hydrocarbon

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2
Q

test to distinguish different hydrocarbons:

A

Bayer’s Test
Br2 Test (light and dark)
Tollen’s Test
Sulfuric acid test

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3
Q

the experiment includes the generation of this

A

ethyne

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4
Q

used to determine the presence of ethyne

A

flammability test

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5
Q

oxidizes alkenes to geminal diols

A

dilute aqueous potassium permanganate

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6
Q

means two -OH groups

A

diol

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7
Q

OH groups on adjacent carbons

A

geminal

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8
Q

oxidized to geminal diketones

A

alkynes

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9
Q

in this reaction, the potassium permanganate is reduced to this of manganese dioxide

A

brown precipitate

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10
Q

what the potassium permanganate is reduced to

A

manganese dioxide

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11
Q

which solution is the potassium permanganate soluble in

A

water

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12
Q

neither water nor potassium permanganate is soluble in this

A

hydrocarbon

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13
Q

where the water and hydrocarbon reaction takes place and is somewhat slow

A

water-hydrocarbon interface

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14
Q

except cycloalkanes react with bromine

A

unsaturated hydrocarbons

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15
Q

these are the only hydrocarbons that is negative in br2 (dark)

A

alkane

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16
Q

hydrocarbons positive in Br2 (light)

A

all hydrocarbons

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17
Q

usually used as solvents because they are unreactive toward both bromine and hydrocarbons that have multiple bonds

A

cyclohexane/carbon tetrachloride/tetrachloromethane

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18
Q

undergo an addition reaction with bromine

A

alkenes and alkynes

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19
Q

its bond becomes a single bond and one bromine atom becomes bonded to each of the carbons that had shared the double bond

A

alkene

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20
Q

its bond undergoes addition becoming a single bond but the carbons that had been joined by the number of its bond will now hold two bromine atoms

A

alkyne

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21
Q

react with concentrated sulfuric acid at room temperature to produce alkyl sulfonic acid

A

alkenes

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22
Q

highly polar and is soluble in the polar sulfuric acid with sufficient stirring

A

alkyl sulfonic acid

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23
Q

not soluble in the polar concentrated sulfuric acid concentrated sulfuric acid, but dissolves as it reacts and the mixture is stirred

A

alkene

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24
Q

not capable of forming
hydrogen bonds, while the sulfuric
acid and the alkyl sulfonic can

A

alkene

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25
Q

especially strong
type of dipole-dipole attraction

A

hydrogen bonding

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26
Q

in order for the H-bonding to occur:

A

➢ one of the molecules must
have a hydrogen (directly)
bonded to a fluorine, oxygen,
or nitrogen

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27
Q

will be strongly attached
to a fluorine, oxygen, or nitrogen in
another molecule

A

hydrogen

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28
Q

more reactive than saturated counterpart

A

unsaturated hydrocarbons

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29
Q

strong oxidative
reagent that lead to the formation of
alcohol for alkenes and carboxylic
acid for alkynes

A

Bayer’s reagent

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30
Q

weak oxidizing
agent composed of ammoniacal
silver nitrate

A

Tollen’s reagent

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31
Q

Reacts with terminal alkynes
to form silver alkyides

A

Tollen’s reagent

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32
Q

addition of halide
substituents like bromine

A

halogenation

33
Q

Occurs via different
mechanisms and extent with
different hydrocarbons

A

halogenation

34
Q

Materials and reagent needed (9)

A

➢ Hexane
➢ cyclohexene
➢ Calcium carbide
➢ Unknown hydrocarbon 1
➢ Unknown hydrocarbon 2
➢ Bromine in CCl4
➢ Bayer’s reagent
➢ Distilled water
➢ Tollen’s reagent

35
Q

Equipment needed (6)

A

➢ Pasteur pipettes
➢ Screw-capped test tubes
➢ Separatory funnel
➢ Distilling flask
➢ Iron ring and clamp
➢ Rubber tubing and pinchcock

36
Q

are combustible,
avoid skin contact and inhalation of
vapour

A

hydrocarbons

37
Q

its generation its highly
exothermic

A

acetylene

38
Q

has an explosive
tendency when it forms alkylide
precipitates

A

Tollen’s reagent

39
Q

Dilute with copious amount of
water and dispose of it
immediately

A

Tollen’s reagent

40
Q

5 drops of the following in separate
test tubes:

A

➢ Hexane
➢ Cyclohexene
➢ Unknown hydrocarbon 1
➢ Unknown hydrocarbon 2

41
Q

procedures of bayer’s test (2 steps)

A

➢ 5 drops of Bayer’s reagent to
each sample
➢ Shake and observe

42
Q

procedures of bromination (with light)

A

➢ Add 5 drops of bromine
➢ Shake and observe

43
Q

procedures of bromination (without light)

A

➢ Wrap the test tube with paper
➢Add 5 drops of bromine and immediately place the sample in a dark place for 2 minutes
➢Observe

44
Q

procedures of tollen’s test

A

Add 5 drops of Tollen’s reagent
Shake and observe

45
Q

label the setup of acetylene generation

A

grade yourself accordingly

46
Q

acetylene generation setup (4) steps

A

➢Add small increments of water to calcium carbide at a time to initiate formation
➢Collect acetylene into test tubes by inserting the end of the rubber tubbing and opening the pinchcock
➢When enough acetylene is collected, cap the tubes immediately
➢Observe any ensuing reaction

47
Q

used to identify the presence of unsaturation (double or triple bonds) in hydrocarbon compounds

A

bayer’s test

48
Q


Detects the presence of carbon-carbon double or triple bonds

A

bayer’s test

49
Q

bayer’s reagent is a mixture of

A

concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4)

50
Q

nitric acid

A

HNO3

51
Q

sulfuric acid

A

H2SO4

52
Q

the reaction between the reagent and hydrocarbon if unsaturation is present

A

reddish-brown color

53
Q

Baeyer’s reagent result if the solution is pinkish purple

A

negative (alkene and alkyne are absent)

54
Q

Bayer’s reagent solution discharges color and a brown sludge is formed

A

positive (alkene and alkyne are present)

55
Q

color change in bayer’s test is because of this process in the unsaturated bonds in the hydrocarbon by the nitric acid reagent

A

oxidation

56
Q

formed when the unsaturated bond react with the nitric acid that causes a rearrangement of electrons

A

nitro compound

57
Q

result of bayer’s test:

Hexane –
Cyclohexene –
Acetylene –

A

Hexane – negative
Cyclohexene – positive
Acetylene – positive

58
Q

result of br2 test (light)

A

all positive

59
Q

result of br2 test (dark)

A

Alkane is negative in Br2

60
Q

used to detect the presence of unsaturation, particularly carbon-carbon double or triple bonds

A

br2 test

61
Q

Hydrocarbon is mixed with what in br2 test

A

bromine water

62
Q

solution of bromine (Br2) dissolved in water

A

bromine water

63
Q

reddish-brown liquid at room temperature

A

bromine

64
Q

this result in br2 indicates a positive result for unsaturation in the hydrocarbon

A

colorless solution or color change

65
Q

what color in br2 test for saturated carbons

A

orange colored

66
Q

what color in br2 test for unsaturated carbons

A

colorless

67
Q

Result for bromine water test (dark)
Hexane –
Cyclohexene –
Acetylene –

A

Hexane – no reaction
Cyclohexene – positive result
Acetylene – positive result

68
Q

Result for bromine water test (light)
Hexane –
Cyclohexene –
Acetylene –

A

all positive

69
Q

used to distinguish between an aldehyde and a ketone

A

Tollen;s test

70
Q

positive for tollen’s test

A

dark grey precipitate or silver mirror

71
Q

negative for tollen’s test

A

no result

72
Q

which hydrocarbon will be positive for tollen’s

A

alkyne

73
Q

involves the oxidation of unsaturated bonds in hydrocarbons by the nitric acid reagent

A

bayer’s oxidation

74
Q

refers to the reaction between a hydrocarbon and bromine (Br2) in the presence of light.

A

bromination

75
Q

state the reaction between alkene and KMnO4 and H2O

A

grade yourself accordingly

76
Q

used to detect aldehydes and distinguish them from ketones.

A

tollen’s test

77
Q

can be used to distinguish between an alkane and alkene/alkyne through the color test

A

bromine test

78
Q

state the reaction between ethylene and bromine

A

grade yourself accordingly

79
Q

state the reaction between aldehyde and tollen’s reagent

A

grade yourself accordingly