organic

Question 1

hydrocarbon

Answer 1

organic compound that contains only carbon & hydrogen

Question 2

saturated molecule

Answer 2

molecule that contains only C-C bonds

(substitution reactions)

Question 3

unsaturated molecule

Answer 3

molecule that contains C=C or C≡C bonds

(addition reactions)

Question 4

structural isomerism

Answer 4

molecules with identical molecular formulae, but different atomic structures

i.e. chain & positional isomers

Question 5

geometric isomerism (stereoisomerism)

Answer 5

molecules with identical molecular formulae, but different spatial arrangements of atoms

i.e. when both carbons in a C=C bond (alkene) are attached to two different groups

cis-isomer : vertical symmetry

trans-isomer : vertical asymmetry

Question 6

relationship between mass & dispersion forces

Answer 6

↑mass = ↑electrons = ↑dispersion forces

Question 7

relationship between carbon chain length & dispersion forces

Answer 7

↑length = ↑surface area = ↑dispersion forces

Question 8

even-numbered vs odd-numbered carbon chains

Answer 8

even-numbered carbon chains pack more tightly than odd-numbered carbon chains

∴ stronger dispersion forces

∴ greater boiling/melting point

Question 9

straight vs branched carbon chains

Answer 9

straight carbon chains pack more tightly than branched carbon chains

∴ stronger dispersion forces

∴ greater boiling/melting point

Question 10

markovnikov’s rule

Answer 10

when alkenes undergo addition reactions with H₂O or hydrogen halides, hydrogen joins the carbon of the C=C bond with more hydrogen (major product)

small proportion of products may oppose this rule (minor product)

Question 11

primary, secondary & tertiary alcohols

Answer 11

primary : OH attached to a carbon with at least two hydrogen

secondary : OH attached to a carbon with one hydrogen

tertiary : OH attached to a carbon with no hydrogen

Question 12

relationship between carbon chain length & hydrogen bonding

Answer 12

↑length = ↓hydrogen bonding attraction

∵ ↑overall non-polar nature

Question 13

relationship between alcohol type & physical properties

Answer 13

boiling point : primary > secondary > tertiary

solubility : tertiary > secondary > primary

∵ branching - OH becomes less accessible to form hydrogen bonds

Question 14

relationship between chain length & alcohol solubility

Answer 14

↑length = ↓solubility

∵ non-polar hydrocarbon chain becomes stronger

Question 15

why are carboxylic acids more acidic than alcohols ?

Answer 15

hydrogen atom is more exposed

∴ greater ability to donate a proton (↑Kₐ )

Question 16

intermolecular forces of carboxylic acids

Answer 16

two molecules of carboxylic acid can form a dimer connected by two hydrogen bonds

∴ stronger hydrogen bonding

∴ stronger dispersion forces (doubled mass)

Question 17

why are carboxylic acids more soluble than alcohols ?

Answer 17

COOH is more hydrophilic than OH

∵ both CO & OH can hydrogen bond with H₂O

Question 18

intermolecular forces of haloalkanes

Answer 18

dispersion forces & dipole-dipole attractions

∵ C-halogen bonds have high differences in electronegativity

Question 19

aldehydes

Answer 19

C=O in a terminal position

Question 20

ketones

Answer 20

C=O in a non-terminal position

Question 21

intermolecular forces of aldehydes & ketones

Answer 21

dispersion forces & dipole-dipole attractions

∵ ↑electronegative oxygen (polar C=O bond)

Question 22

intermolecular forces of esters (COO)

Answer 22

dispersion forces & dipole-dipole attractions

esters can accept hydrogen bonds from H₂O, but itself cannot hydrogen bond with H₂O

∵ no hydrogen atom

∴ slightly soluble from polarity, but less soluble than carboxylic acids

Question 23

basicity of amines

Answer 23

amines accept H⁺ if reacted in solution (brønsted-lowry base)

e.g. ethylamine + H⁺ → ethylammonium ion

Question 24

intermolecular forces of amines

Answer 24

dispersion forces & hydrogen bonding

highly polar amino group capable of forming multiple hydrogen bonds

∴ high boiling point

∴ high solubility

Question 25

functional group priorities

Answer 25

carboxyl > ester > amide > nitrile > carbonyl (aldehyde) > carbonyl (ketone) > hydroxyl > amino > alkene > alkyne > halo

Question 26

alkane reactivity

Answer 26

unreactive ∵ strong sigma bond - - - substitution reactions with halogens (UV) to form haloalkanes combustion reactions with O₂ to produce CO₂, H₂O & heat

Question 27

alkene reactivity

Answer 27

↑reactivity than alkanes ∵ weak pi bond - - - reduction reactions with H₂ (Ni/heat) to form alkanes addition reactions with H₂O (H₃PO₄/heat) to form alcohols addition reactions with halogens (e.g. Br₂) to form dihaloalkanes addition reactions with hydrogen halides (e.g. HBr) to form haloalkanes

Question 28

addition polymerization

Answer 28

monomers undergo addition reactions (catalyst/heat) to form polymers e.g. ethene → polyethene

Question 29

combustion of alcohols

Answer 29

alcohol + O₂ → CO₂ + H₂O + energy

Question 30

oxidation of alcohols

Answer 30

oxidation reactions with K₂Cr₂O₇/KMnO₄ (H⁺/heat) to form : primary : aldehyde secondary : ketone tertiary : inert (no replaceable hydrogen)

Question 31

esterification of alcohols

Answer 31

alcohol + carboxylic acid → ester + H₂O (H₂SO₄) e. g. methanol + propanoic acid → methyl propanoate + H₂O - - - hydrolysis : opposite of condensation ester + H₂O → alcohol + carboxylic acid (dilute H₂SO₄/heat)

Question 32

haloalkane reactivity

Answer 32

elimination reactions with NaOH (heat) to form alkenes substitution reactions with NaOH to form alcohols substitution reactions with KCN (ethanol/heat) to form nitriles (C≡N) substitution reactions with NH₃ to form amines (NH₂) substitution reactions with halogens to form dihaloalkanes

Question 33

aldehyde & ketone reactivity

Answer 33

aldehyde : oxidation reactions with K₂Cr₂O₇/KMnO₄ (H⁺/heat) to form carboxylic acids ∵ terminal C=O (replaceable hydrogen) ketones cannot oxidize ∵ non-terminal C=O (no replaceable hydrogen)

Question 34

nitrile reactivity

Answer 34

reduction reactions with H₂ (Ni/heat) to form amines (NH₂) e.g. ethanenitrile + H₂ → ethanamine

Question 35

amine reactivity

Answer 35

condensation reactions with carboxylic acids to form amides (CONH₂) e.g. methanamine + ethanoic acid → methylethanamide + H₂O

Question 36

bromine water test

Answer 36

alkene : brown → colorless alkane : brown → brown

Question 37

acidified potassium dichromate test

Answer 37

1° & 2° alcohol : orange → green 3° alcohol : orange → orange

Question 38

acidified potassium permanganate

Answer 38

1° & 2° alcohol : purple → colorless 3° alcohol : purple → purple