Organic chemistry Flashcards
Homologous series properties
- same functional group
- common general formula
- prepared by same method
- undergo similar chemical reactions
- each member differs from next by a CH2 group
- show a trend in physical properties
What is a Hydrocarbon
Organic compound consisting of hydrogen & oxygen only.
- When burnt completely in air, H2O & CO2 are formed
What are isomers
Organic compounds having same molecular formula but different structural formulae ; having same chemical properties but different physical properties
Obtaining alkanes
Fractional distillation of crude oil ( petroleum ) in an oil refinery
Physical properties of alkanes
1) non-conductors of electricity
2) insoluble in water
3) as we move down the series, increase in Van Der Waals force causes :
- change in state
- increase in MP & BP
- increase in density
- increase in viscocity
- decrease in volatility
- decrease in flammability
Chemical properties of alkanes
- combustion reaction
( burning in air ) - substitution reactions
Obtaining alkenes
- cracking of big alkanes
- dehydration of alcohols
Physical properties of alkenes
Same as alkanes
Chemical properties of alkenes
- Combustion
- Hydrogenation
- Halogenation
- Hydrogen halides
- Hydration reaction
Hydrogenation reaction
Conditions
- nickel catalyst
- 180^C
Halogenation reaction
- chlorination reaction
- bromination reaction
- iodination reaction
Hydration reaction
Conditions
- phosphoric acid catalyst
- 300^C
- 65atm
Test for alkenes
- decolourise aqueous bromine ( red brown -> colourless )
Uses of alkenes
-> To make alcohols
Conditions
- H3PO4 catalyst
- 300^C
- 65atm
-> to make plastics
Formation of alcohol
- Fermentation of glucose
- Hydration of ethene
Physical properties of alcohols
1) soluble in water
2) non-conductors of electricity
3) highly flammable liquids
4) volatile liquids
5) as we move down the series, an increase in Van Der Waals forces causes :
- increase in MP & BP
- increase in density
- increase in viscocity
- decrease in volatility
- decrease in flammability
Chemical reactions of alcohols
- Combustion
- Dehydration reaction
- Oxidation reaction
- Esterification reaction
- react with reactive metals to to liberate H2 gas
Test for alcohols
- turn acidified K2CR2O7 from orange -> green
- decolourise acidified KMnO4
- give sweet fruity smell when warmed with an organic acid in presence of concentrated H2SO4 catalyst
Formation of organic acids
- oxidation of alcohols
Chemical reactions of organic acids
- combustion
- react with reactive metals to liberate H2 gas with effervescence
- react with carbonates & bicarbonates to liberate CO2 gas with effervescence
- neutralise metallic oxides ( basic oxides )
- neutralise alkalis
- undergo esterification by warming with alcohols in the presence of few drops of concentrated H2SO4 catalyst ; esters formed ; sweet fruity smell
Uses of esters
- perfumes
- solvents
- food flavourings
Test for organic acids
- turn blue litmus paper red
- chemical reactions above
