Organic Chemistry Part 1 Flashcards
What are hydrocarbons
Organic compounds that only contain hydrogen and carbon
What is a homologous series
A family of organic compounds with the same functional group and similar chemical properties
Examples: Alkanes, alkenes etc.
What is a functional group
An atom or group of atoms that give a molecules its characteristic chemical properties
What are functional groups of alkanes, alkenes, alcohols and carboxylic acids
Alkanes have no functional group
Alkenes have carbon-carbon double bond
Alcohols have hydroxyl group
Carboxylic acids have carboxyl group
What are characteristics of homologous series
Have same general formula
Similar chemical properties
Show gradual change in physical properties down the series from one member to the next
Successive members in series differ from each other by a -CH2- group
How does melting and boiling point vary down a homologous series
The larger the relative molecular mass, higher the melting and boiling points. More energy is required to overcome the stronger intermolecular forces of attraction between the larger molecules
How does viscosity of liquid vary down a homologous series
The larger the relative molecular mass, the more viscous the compound is. This is due to the stronger intermolecular forces of attraction between larger molecules
What is a saturated compound
A compound containing only single bond between carbon atoms
What is an unsaturated compound
A compound containing at least a double or triple bond between carbon atoms
Name the prefixes of organic compound up to 10 (number of carbon atoms in each molecule)
meth-, eth, prop-, but-, pent-, hex-, hept-, oct-, non-, dec-
How is crude oil separated in oil refinery
Separated into useful fractions by fractional distillation. Each fraction is mixture of hydrocarbons which boils over certain temperature range. Lighter fraction contains molecules with fewer carbon atoms and lower boiling point range than heavier fraction. Lighter fractions come out at higher ‘outlets’ of fractionating column
Describe fractional distillation of crude oil
Crude oil heated to 400C in furnace and boiling takes place. Vapours passed into fractionating column. Fractionating column is hottest at bottom and cooler at top. Hot vapours rise up column, cool and condense at different heights and collected at respective outlet. Lighter fractions with lower boiling point are collected at top of column as gases. Heavier fractions with higher boiling points are collected at the bottom of the column as residue.
Define catalytic cracking
A process to break down long-chain hydrocarbons into shorter chain hydrocarbons by passing the hot vapourised hydrocarbons over a heated catalyst
What are the conditions for catalytic cracking
Catalyst is aluminium oxide and silicon dioxide at high temperature of about 500C to 700C. Pressure is about 1atm.
Rate of cracking and end products strongly dependent on temperature and presence of catalyst used
What is the importance of cracking
Converts heavy crude oil fractions like lubricating oil which are high in supply but low in demand into lighter fractions like petrol which is low in supply but high in demand
Used to produce large amounts of shorter chain alkenes which are used to make useful chemicals (e.g. plastic, ethanol)
Cracking used to produce hydrogen, used in manufacture of ammonia in Haber process or hydrogen fuel cells
What are issues related to competing uses of crude oil fractions
Non-renewable resource is used as fuel(90%) and chemical feedstock(10%)
If more crude oil used as energy source, less available for producing chemicals. Shortage of crude oil will lead to shortage of chemicals
What are ways to conserve crude oil
Reduce number of motor vehicles on the road by taking public buses or MRT, driving smaller cars which consume less petrol, improve design of power stations and vehicles for efficient use of crude oil, alternative energy sources
What are alternative fuels to crude oil
Biofuels - renewable energy source which comes from plants/animals, replaced relatively quickly
Bioethanol - fermentation of sugar in sugarcane plants, plants can be regrown/replaced in short period of time, burning bioethanol more environmentally sustainable, as sugar cane grows, absorbs carbon dioxide through photosynthesis, offsetting CO2 produced when bioethanol burnt
What are issues with using bioethanol as fuel
Producing enough bioethanol requires significant cultivation, harvesting and transportation of sugarcane. Processes often use fossil fuels, increasing CO2 emissions. Crucial to consider CO2 generated during product and transportation when accessing environmental impact of biofuels
What are alkanes(not a definition)
Saturated hydrocarbons which have the general formula CnH2n+2 (starts with n=1)
What are the names for common side chains:
CH3
C2H5
C3H7
C4H9
Methyl
Ethyl
Propyl
Butyl
What are names for common side chains:
F
Cl
Br
I
Fluoro
Chloro
Bromo
Iodo
How to name branched-chain alkanes
Name longest carbon chain(parent chain)
Name side chain
Label position of side chain to C on parent chain
Add side chain name to parent chain
Use prefixes to indicate multiple of same type of side chains present
When there are multiple side chains, order in ALPHABETICAL order
Define structural isomer
Structural isomers have same molecular formula but different structural formula
(Isomers have different properties such as melting points)
What are physical properties of alkanes and alkenes
Insoluble in water, soluble in organic solvent, (melting and boiling point, viscosity from general homologous series trend0
Describe combustion as chemical property of alkane
Alkanes burn readily in air when ignited by spark of flame. Combustion of alkanes are highly exothermic
Complete combustion of alkanes produces water and CO2 due to sufficient air(oxygen)
Incomplete combustion produces water and carbon/carbon monoxide due to insufficient O2
Describe flammability of alkanes
Larger the relative molecular mass, less flammable the alkane becomes. As percentage of carbon present increases, it is more difficult to burn alkane. Flame produced tends to be more sooty
Define substitution reaction
Involves the direct replacement of an atom in a molecule with another atom. (Alkanes react with halogens in presence of UV light.)
Describe reaction of methane with chlorine
Each hydrogen atom in methane substituted one at a time by one of two chlorine atoms in Cl2. Remaining chlorine atom from Cl2 will form hydrogen chloride gas with hydrogen atom that was substituted. Other products include mixture of four types of chloromethane molecules, with relative amounts dependent upon time that reaction is allowed to proceed
What are alkenes(not a definition)
Unsaturated hydrocarbons which have general formula of CnH2n (starts with n=2)
What can you infer from number “1” in “but-1-ene”
The number represents location of carbon atom on parent chain where carbon-carbon double bond is located
Describe combustion as chemical property of alkenes
Alkenes burn in excess air to produce carbon dioxide and water vapour. Alkenes contain relatively higher percentage of carbon than alkanes with same number of carbon atoms. Alkenes are more likely to undergo incomplete combustion, producing carbon monoxide and carbon. Alkenes burn with sootier flame than corresponding alkanes
Describe addition reaction
In addition reaction, substance is added across the carbon-carbon double/triple bond in unsaturated organic compound to form new compound
Describe hydrogenation
Addition of hydrogen to alkenes to form alkanes
Conditions are 180C and nickel catalyst
What is application of hydrogenation
