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