7.2 Hydrocarbons

Question 1

haloalkanes are…

Answer 1

alkanes where H atoms are replaced by a halogen

Question 2

naming haloalkanes

Answer 2

(1) place halo functional group at the front, alphabetically
(2) add “o” to the stem e.g. bromine = bromo

Question 3

highest and lowest priority functional groups

Answer 3

highest = carboxyl group
lowest = halo group

Question 4

alcohols contain what functional group

Answer 4

-OH

Question 5

naming alcohols

Answer 5

ending e –> ending ol

methane –> methanol
but-1-ene –> but-1-ol

Question 6

explain primary, secondary, tertiary alcohols

Answer 6

depends on how many other Carbon atoms the -COH has bonded with

Question 7

primary amines contain what functional group

Answer 7

amino functional group -NH2

Question 8

naming primary amines

Answer 8

ending e –> amine

ethane –> ethanamine

Question 9

secondary and tertiary amines

Answer 9

N-methyl…
N,N-dimethyl…

Question 10

amines produce … in dissolution

Answer 10

alkylammonium and hydroxide ions

Question 11

amines + acid –>

Answer 11

alkylammonium salts + nonmetal ion

Question 12

amines are weak/strong bases

Answer 12

WEAK, due to the lone pair of electrons on their N atoms… and somewhat polar

Question 13

amides are … [acidity]

Answer 13

neutral

Question 14

carboxyl functional group is

Answer 14

-CO

Question 15

aldehyde vs ketone

Answer 15

aldehyde has carboxyl group AT THE END of the hydrocarbon chain

ketone has carboxyl group IN THE MIDDLE

Question 16

naming aldehydes

Answer 16

ending e –> ending al or using -dehyde

propane –> propanal

Question 17

naming ketones

Answer 17

ending e –> one

butane –> butanone

Question 18

what is the simplest ketone?

Answer 18

propanone CH3 COCH3
aka acetone

Question 19

carboxylic acids contain functional group…

Answer 19

-COOH
(at end of the chain)

Question 20

naming carboxylic acids

Answer 20

ending E –> OIC acid

ethane –> ethanoic acid

Question 21

primary amides contain…

Answer 21

carboxyl functional group connected to amino functional group

Question 22

naming amides

Answer 22

ending E –> ending AMIDE

methane –> methanamide

Question 23

what are esters

Answer 23

product of alcohol and carboxylic acid

Question 24

naming esters

Answer 24

-COO- (C)
(in middle of chain)

Question 25

ester equation

Answer 25

alcohol + carboxylic acid ⇌ ester + water

Question 26

naming esters

Answer 26

ending E --> OATE alcohol + carboxylic acid ethanol + propanoic acid ⇌ ethyl propanoate (pineapple)

Question 27

order of 9 priority functional groups

Answer 27

carboxyl amide carbonyl (aldehyde) carbonyl (ketone) hydroxyl amine alkene alkyne halo

Question 28

force between, polarity, and boiling pt of alkanes

Answer 28

dispersion forces (weak) non-polar low boiling point

Question 29

boiling and melting point of hydrocarbons depends on…

Answer 29

number of carbon atoms (chain length)

Question 30

melting point for odd number carbons vs even number carbons

Answer 30

even number carbons pack more efficiently in solid state = stronger dispersion forces = requires more energy to melt = steeper increase in melting point increment on a MP graph

Question 31

alkene BP is lower/higher than alkanes

Answer 31

LOWER

Question 32

the more branching, the __ the BP

Answer 32

LOWER smaller dispersion forces for less compact hydrocarbons

Question 33

order of highest BP of hydrocarbons

Answer 33

alkene < alkane < alkyne

Question 34

why alkyne BP is highest

Answer 34

electrons making up bonds are more polarisable = stronger London dispersion forces = higher BP

Question 35

hydrocarbon density >/< water

Answer 35

LESS than water

Question 36

solute can dissolve in solvent if…

Answer 36

solute-solvent intermolecular forces are similar to solute-solute and solvent-solvent

Question 37

what happens when you introduce halogen to hydrocarbon

Answer 37

larger electronegativity difference = more polar = more soluble

Question 38

the longer the hydrocarbon chain =

Answer 38

greater dispersion forces = less soluble

Question 39

what is volatility

Answer 39

ease which substance enters gaseous state (boiling pt)

Question 40

what is flash point

Answer 40

minimum temp. which small flame causes the vapour above a liquid in enclosed area to ignite

Question 41

the higher molecular mass, the higher BP, the … flash pt

Answer 41

higher

Question 42

ignition temperature is…

Answer 42

temp. substance needs to be heated before spontaneous combustion occurs (of fuel-oxidiser mixture)

Question 43

hydrocarbon fuels are stored and transported as … because …

Answer 43

as LIQUIDS because they occupy smaller volumes than gaseous state - under pressure to keep liquefied

Question 44

haloalkanes have higher/lower? BP than hydrocarbons because …

Answer 44

HIGHER BP because dipole-dipole attraction > just dispersion forces

Question 45

are hydrocarbons miscible with water and why

Answer 45

NO because hydrocarbons are less dense than water large difference in attraction of solute-solute and solvent-solvent intermolecular forces

Question 46

when will organic-organic be miscible?

Answer 46

NP+NP or P+P are miscible (similar forces of attraction)

Question 47

difference between haloalkanes and CFCs

Answer 47

haloalkanes = one or more H is replaced by halogen chlorofluorocarbons = haloalkanes that only contain carbon, Cl, F

Question 48

halons

Answer 48

only contains carbon, bromine + other halogens

Question 49

why CFC depletes ozone layer

Answer 49

decomposition of CFC releases Cl atoms which catalyse ozone depletion

Question 50

why HCFCs are banned

Answer 50

hydrochlorofluorocarbons mostly break down in atmosphere BUT small portion decomposes in stratosphere and can still release Cl atoms

Question 51

why HFCs are banned

Answer 51

hydrofluorocarbons = no Cl means ozone-destroying capacity is 0 BUT got banned bc it's a strong greenhouse gas

Question 52

why CFC effect on ozone layer is seasonal (Antarctica's ozone hole)

Answer 52

winter is dark and cold, no heat or light energy to decompose Cl2 gas spring sunlight splits Cl2 gas into 2 Cl atoms (destroys ozone at greater rate)

Question 53

how to test for C=C double bonds differentiate from C-C single bond

Answer 53

use bromine water (Br2 + water) OR bromine dissolved in organic solvent e.g. hexane WITHOUT THE PRESENCE OF UV LIGHT bc that'll decolourise both alkenes and alkanes

Question 54

what colour is bromine

Answer 54

orange-red

Question 55

how to test for carboxyl functional group

Answer 55

carbonates, indicators, and alcohols

Question 56

carbonate + carboxylic acid test reaction

Answer 56

NaHCO3 carbonate salt + acid --> organic salt + CO2 + water FIZZING, effervescence via limewater test

Question 57

organic acid + alcohol produces…

Answer 57

fruity ester

Question 58

how to test for hydroxyl functional group i.e. alcohol

Answer 58

dry sample + metallic sodium --> product + H2(g) slow BUBBLES

Question 59

why alcohol mustn't contain water when testing it with metallic sodium

Answer 59

sodium metal reacts violently with water

Question 60

1st and 2nd alcohols can be oxidised by…

Answer 60

acidified potassium dichromate (K₂Cr₂O₇) or potassium permanganate (KMnO₄)

Question 61

primary alcohol oxidises to…

Answer 61

aldehyde, then carboxylic acid

Question 62

primary/secondary alcohol w/ K2Cr2O7 colour change on heating

Answer 62

orange to green

Question 63

primary/secondary alcohol w/ KMnO4 colour change on heating

Answer 63

purple to colourless

Question 64

how to test for tertiary alcohol

Answer 64

fast reaction with ZnCl2/HCl mixture secondary is slow reaction primary has no reaction