3.3.1 Introduction to organic chemistry

Question 1

what is the impirical formula ?

Answer 1

Simplest whole-number ratio of atoms of each element in a compound

Question 2

what is a homologus series

Answer 2

a series of compounds w same general formula
- they have same general formula that defines the compounds properties
- they show a gradual variation in physical properties, eg their boiling points.
-they have similar chemical properties

Question 3

what is a molecular formula

Answer 3

formula that tells you the actual number of atoms of the element in a compound

Question 4

each of the type of formulas

Answer 4

displayed formula - c-h-c (fully drawn out formula)
structural formula= CH3CH2CH3

Question 5

which free radical initiation produces which

Answer 5

homolytic fission produces 2 free radicals , in a 2cl out comes 2 cl free radicals
in Heterolytic fission ions are produced

Question 6

what is a free radical

Answer 6

a reactive species which possess an unpaired electron, no charge

Question 7

which form of fission is more common

Answer 7

Most organic reactions occur via heterolytic fission, producing ions

Question 8

what is structural isomerism

Answer 8

compounds with same molecular formula different structures (or structural formulae

Question 9

what types of structural isomerism is there

Answer 9

*Chain isomerism - Compounds with the same molecular formula but different structures of the carbon skeleton

*Position isomerism - Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton

*Functional group isomerism- Compounds with the same molecular formula but with atoms arranged to give different functional groups

Question 10

what is a stereoisomer

Answer 10

molecules with the same structural formula but the atoms are arranged differently in space

Question 11

difference between trans and cis isomers

Answer 11

Cis isomers have the hydrogens on the same side of the carbon
trans isomers have the hydrogens on the opposite sides of the carbon

Question 12

what has to happen to have trans/cis isomers

Answer 12

each carbon atom must be bonded to 2 diff groups , on one side a carbon cant be bonded to H and H
but each carbon must be bonded to min 1 hydrogen

Question 13

whats an alkane

Answer 13

Alkanes are saturated hydrocarbons.

Question 14

fractional distillation

Answer 14

Oil is vapourised then passed into column.
* The fractions condense at different heights *
* The bottom hotter
* The separation depends on boiling point.
* boiling point depends on size of molecules.
* The larger the molecule= larger van der waals forces
* Similar molecules (size, bp, mass) condense together
* Small molecules condense at the top at lower temperatures

Question 15

what is cracking

Answer 15

conversion of large hydrocarbons to smaller hydrocarbon molecules by breakage of C-C bonds

Question 16

which cracking produces a high percentage of alkenes

Answer 16

Thermal cracking produces a higher percentage of alkenes

Question 17

catalytic cracking

Answer 17

.Catalytic cracking happens at a slight pressure, high temperature (450)
.with a zeolite catalyst
. used mainly to produce motor fuels +aromatic hydrocarbons , produces branched and cyclic hydrocarbons too

Question 18

what is zeolite catalyst made of

Answer 18

(sodium aluminate and sodium silicate.)

Question 19

thermal cracking

Answer 19

high temp +pressure (7000KPA and 400-900C)
produces just mainly alkenes

Question 20

Economic reasons for cracking

Answer 20

.The petroleum fractions with shorter C chains (e.g. petrol and naphtha)in more demand than larger fractions.

• To make use of excess larger hydrocarbons and to supply demand for shorter ones, longer hydrocarbons are cracked.
• The products of cracking are more valuable than the starting materials(e.g. ethene used to make poly(ethene),branched alkanes for motor fuels,

Question 21

how are alkanes used as fuels

Answer 21

releases heat energy when burnt
Alkanes readily burn in the presence of oxygen. This combustion of alkanes is highly exothermic,

incomplete combustion produces less energy per mole

Question 22

the pollutants and why they’re bad

Answer 22

Nitrogen oxides-NO is toxic and can form acidic gas NO2 NO2is toxic and acidic and forms acid rain

Carbon monoxide- toxic and contributes to respiratory problems

Unburnt hydrocarbons- Contributes towards formation of smog

soot(carbon)- Global dimming and respiratory problems

Question 23

what are the potential products of incomplete combustion

Answer 23

Co or C + H2O

Question 24

sulfur dioxide -

Answer 24

Sulfur containing impurities are found in petroleum fractions which produce SO2 when they are burned.

SO2 dissolve in atmospheric water and can produce acid rain - damage environment + erodes + damages buildings

coal also high in SO2

Question 25

Flue -gas desulphurisation -

Answer 25

calcium oxide -SO2 + CaO to form CaSO3 then reacted on to form calcium sulphate (CaSO4) - Gypsum - used in plastering so money made from the waste products

Question 26

catalytic converters

Answer 26

cross section mesh of Platinum or Rh (large SA)
2CO + 2NO —> 2CO2 +N2
2NO —> N2 + O2

or even the NO reacted with more unburnt hydrocarbon to form N2 CO2 and H20

Question 27

in nomenclature what applies as a methyl ethyl group

Answer 27

a methyl group only applies in nomenclature if its not on the end of the carbon chain , there must be a carbon either side to it - a methyl group cannot be on the endeg:
C-C-CH3- C