Topic 6: Organic I

Question 1

General formula

Answer 1

Algebraic formula that can describe any member of a family of compounds

Question 2

Empirical formula

Answer 2

Simplest whole ration number of atoms of each element in a compound

Question 3

Molecular formula

Answer 3

Actual number of atoms of each element in a molecule

Question 4

Structural formula

Answer 4

Shows the arrangement of atoms carbon by carbon, with attached hydrogens and functional groups

Question 5

Skeletal formula

Answer 5

Shows bonds of the carbon skeleton only, with any functional groups
H atoms aren’t shown, C’s are vertices

Question 6

Displayed formula

Answer 6

Shows how ll the atoms are arranged and ALL of the bonds between them

Question 7

IUPAC nomenclature rules

Answer 7

1. Find longest carbon chain to name alkane
2. Identify functional groups and number Cs so that they are as small as possible
3. Assign location of group using n° and place, then assemble in alphabetical order

Question 8

Structural isomerism

Answer 8

Same molecular formula but different structural formula among atoms
chain, position or functional
They have different physical and chemical properties

Question 9

Stereoisomers

Answer 9

Same molecular and structural formula but different spatial orientation of groups in the molecule
E-Z isomerism: restricted rotation about double bonds
Two different groups on each carbon of the C=C bond, highest atomic n° is the priority
Same side: Z (cis - if priority groups are equal)
Different side: E (trans)

Question 10

Aldehydes

Answer 10

R-C=O-H
-anal

Question 11

Ketones

Answer 11

R2-C=O-R1
R2+R1 = starting molecule
-anone
E.g ethanone

Question 12

Alkanes

Answer 12

CnH2n+2
Saturated hydrocarbons, only single covalent bonds
Main constituents of crude oil, used as fuel
Need to be reformed as straight chain alkanes cause knocking (small explosions in engine, combustion less efficient)
Platinum catalyst to reform into branched and cyclic alkanes

Question 13

Fractionating Column

Answer 13

Petroleum enters vaporised at bottom left
Boiling point decreases as you go up (so each product condenses at a different temp)
Length of carbon chain decreases upwards (volatility is inversely proportional to carbon chain length)
Products: (upwards)
Bitumen, fuel, diesel, kerosene, naphtha, gasoline, refinery gas

Question 14

Thermal Cracking

Answer 14

Decomposition reaction, breaking C-C bonds in long alkanes
Homolytic Fission: free radical reaction
High temp: 450-900°C
High pressure: up to 7000 kPa

Question 15

Catalytic Cracking

Answer 15

High temp: 450°C, pressure slightly above atmospheric pressure (around 100kPa)
Zeolite catalyst (large surface area)
Produces more branched, cyclic and aromatic HCs (more useful for making fuels) so more productive than thermal

Question 16

Free Radical Substitution

Answer 16

Photochemical reaction: UV light provides activation energy
Alkane -> haloalkane + HX
1. Initiation: homolytic fission produces two radicals
2. Propagation: spread of radicals, chain reaction
3. Termination: radicals react together
RADICALS: species with an unpaired electron, highly reactive

Question 17

Pollutants: Carbon Monoxide

Answer 17

incomplete combustion of fuels (road transport)
reacts with haemoglobin & reduces oxygen-carrying capacity of blood
reacts with other gases to form ozone

Question 18

Pollutants: Carbon Dioxide

Answer 18

burning fossil fuels to produce electricity, natural processes e.g respiration
anthropogenic global warming

Question 19

Pollutants: Oxides of Nitrogen

Answer 19

Combustion in road transport
NO -> global warming contributor
NO2 -> ground level ozone forming & component of smog**
SMOG: permanent fog of pollution

Question 20

Pollutant: Sulfur dioxide (SO2)

Answer 20

burning fossil fuels to generate electricity
Smog, produces acid rain and causes breathing problems

Question 21

Catalytic Converters

Answer 21

CO + 2NO -> CO2 + N2
Catalyst: platinum/palladium on honeycomb
1. ADsorption: reactants weakly bond to catalyst surface
2. Reaction: bonds in reactants weakened (shaking), lower Ea needed for chemical reaction
3. DEsorption: products released from catalytic surface

Question 22

Alternative Fuels

Answer 22

to reduce pollution from combustion & due to limited amount of non-renewable
BIODIESEL: refining renewable fats & oils
BIOETHANOL: fermentation
BIOGAS: released when organic waste breaks down
Benefits: carbon neutral, reduce waste in landfills, production gives money to less developed countries where crops are grown
Drawbacks: cost of changing engines, developed countries don’t have enough space for crops

Question 23

Alkenes

Answer 23

CnH2n, unsaturated hydrocarbons, C=C
Decolourise Br water
have stereoisomerism and are functional group isomers to cycloalkanes

Question 24

Bonding in Alkenes

Answer 24

single covalent bonds are sigma, orbitals overlap end-to-end
double covalent bonds have one sigma and one pi bond, sideways bonding of p orbitals with s orbital in the middle

Question 25

Addition reactions of Alkenes

Answer 25

1. Alkenes + halogens -> dihaloalkane 2. Alkenes + steam -> alcohol 3. Alkenes + hydrogen -> alkane (hydrogenation)

Question 26

Electrophilic addition

Answer 26

Electrophile: a species attracted to a negative region Bonded pair goes to negative (when C-H forms, H-X breaks and e- move to X side) HX is electrophile Carbocation formed bond to H is dative as Br- has taken both e- Asymmetric alkenes produce different possible results

Question 27

Carbocations

Answer 27

+ve ion containing a C with a +ve charge depends on number of carbons bonded to the one which has functional group tertiary > secondary > primary in possibility & stability

Question 28

Nucleophilic Substitution

Answer 28

Nucleophile: species that donates an electron pair to form a dative covalent bond It is attracted to the +ve C causing C-X bond to break

Question 29

Nitriles

Answer 29

R-C≡N alkanenitrile useful for extending the carbon chain nucleophilic substitution of :C≡N- ion

Question 30

Elimination of ALKANES

Answer 30

OH- ions dissolved in ethanoic acid (reacts as a base -> proton acceptor) Produces alkane + water + salt

Question 31

ALCOHOLS: halogenation

Answer 31

Chlorination is proof of alcohols using PCl5 at room temp (white steamy fumes from HCl dissolved in water is proof of OH- group) Bromination: HBr and 50% concentrated H2SO4, needs to be warmed up Iodination: red phosphorous and iodine (PI3) heat under reflux (makes phosphoric acid)

Question 32

ALCOHOLS: elimination

Answer 32

catalyst concentrated H3PO4 heat ethanolic solvent produces alkane + water Dehydration of alcohol Double bond can form to either side of C-OH bond, resulting in isomers

Question 33

ALCOHOLS: oxidation

Answer 33

Primary: incomplete produces aldehyde, complete produces carboxylic acid (potassium dichromate acidified with sulfuric acid, heat under reflux) Secondary: reflux, same catalyst but produces ketone Tertiary: no reaction (as there is no C-H bond to break, only C-R) H+;K2Cr2O7 goes from orange to green