Chapter 7 - Organic Chemistry Flashcards
What are the properties of an alkene?
- unsaturated = contain at least one double covalent bond between carbon atoms
- first three alkenes are: ethene propene butene
- methene doesn’t exist!
What is the general formula for alkenes?
CnH2n
What is a homologous series?
A ‘family’ of organic compounds that have the same functional group and similar chemical properties They have the same general formula and follow regular trend for physical properties eg boiling point increases as you go along sequence
Why aren’t alkenes used as fuels?
Less likely to completely combust
Give off a lot of smoke - soot and CO from incomplete combustion
What are the alkene addition reactions
- alkene + water(steam) = alcohol
- alkene + hydrogen = alkane
- alkene + halogen (chlorine/bromine/iodine) = halogenoalkane
What happens when you add bromine water to an alkene?
The alkene reacts with the bromine turning it from an orange-red to colourless
How do we determine if something is an alkane or alkene?
Use bromine water addition reaction because alkanes don’t react
What is the general formula for alkanes?
CnH2n+2
What are the first four alkanes?
Methane, Ethane, Propane, Butane
What are the properties of hydrocarbons?
- The shorter the chain the more runny/less viscous
- The shorter the chain the more volatile (turn into gas at lower temp)
- The shorter the chain the more flammable
- The longer the chain the higher the boiling point
What is the word equation for combustion?
hydrocarbon + oxygen > carbon dioxide + water
What is the word equation for incomplete combustion?
hydrocarbon + (insufficient) oxygen > carbon monoxide + water
How are the hydrocarbons in crude oil separated?
Fractional distillation
What is a fraction in fractional distillation?
Group of similar chain length and similar boiling point
Are long or short chains more useful
Short chains
What is cracking used for?
To break longer chain hydrocarbons into shorter chains
Equation for cracking
long chain alkane > short chain alkane + alkene
What are the two types of cracking
Steam = mix with steam Catalytic = pass it over powered catalyst eg Al2O3
What are the uses of alcohols?
- Drinks
- Perfume
- Solvent
- Antiseptic
- Fuel
What are the first four alcohols?
methanol, ethanol, propanol, butanol
What is the general formula for alcohols?
CnH2n+1OH
What are the two ways ethanol can be produced?
Ethene + steam
Fermentation
What is ethene + steam?
React ethene and steam to produce ethanol
- non-renewable as ethene comes from crude oil
- Requires more energy as oil and water need to be heated
- Continuous process
- Not carbon neutral
- Fast rate
- Conditions: catalyst = phosphoric acid, temp 300, high pressure
- Very pure - 100% only product produced
What is fermentation?
Glucose respires anaerobically to produce ethanol and carbon dioxide
- renewable
- Less energy needed (only 37 degrees)
- Batch process
- Carbon neutral
- Slow rate
- Conditions: catalyst = yeast, temp 37, no oxygen
- Not very pure - only 15% of products is ethanol
What is the word equation for the combustion of alcohol?
alcohol + oxygen > water + carbon dioxide
What is the word equation for the reaction between an alcohol and sodium?
alcohol + sodium > alkoxide (e.g. sodium ethoxide) + hydrogen
What is the word equation for the oxidation of alcohols
alcohol > carboxylic acid
What affects the solubility of alcohols in water?
Chain length - short = more soluble, long = less soluble
What are the 4 homologous series?
alkanes, alkenes, alcohols, carboxylic acids
What are the first four carboxylic acids>
methanoic acid, ethanoic acid, propanoic acid, butanoic acid
What is the general formula for carboxylic acids?
CnH2n+1COOH
What is produced when ethanoic acid is reacted with ethanol?
Ethyl ethanoate + water
What is ethyl ethanoate?
An ester
