3.3 - hydrocarbons Flashcards
explain the difference between unsaturated and saturated hydrocarbons?
a hydrocarbon is saturated if their is a single bond between the carbon atoms, it is unsaturated if it contains a double or triple bond between carbon atoms.
what is a homologous series?
a sequence of compounds with the same functional group and similar chemical properties.
ie. alcohols = hydroxyl group
describe the trends in the physical properties of hydrocarbons.
as the length of the carbon chain (backbone) increases, the melting and boiling points increase.
complete combustion of hydrocarbons.
complete combustion occurs when the supply of oxygen is not limited, the products include carbon dioxide and water.
incomplete combustion of hydrocarbons.
incomplete combustion occurs when there is an insufficient amount of oxygen, the products are water and/or soot (C) and carbon monoxide (CO).
what are the chemical reactions of hydrocarbons determined by?
they are determined by the functional group present.
predict and explain the product of an addition reaction of an alkene.
alkene and alkynes undergo addition reactions due to the presence of double and triple bonds. atoms will add to adjacent atoms either side of the double/triple covalent bond.
when an alkene reacts with bromine water, it will undergo an addition reaction, halogens attack the double bond and remove electrons resulting in the formation of a saturated alkane (haloalkane).
what is an isomer?
hydrocarbons can exist as different structural isomers, they have the same molecular formula but a different structural formula.
isomers are different compounds and consequently have different physical and sometimes chemical properties.
identify a test which can be conducted to determine the difference between an alkane and alkene.
when an alkene is placed into a test tube with bromine water and shaken, it will discolourise , however, if this is done with an alkane it will not discolourise.
describe the physical and chemical properties of alcohols.
the alcohol groups form hydrogen bonds which make short chain molecules soluble in water, solubility in water decreases as chain length increases. - the molecule becomes more and more polar as the length of the carbon chain increases.
alcohols contain hydrogen bonds, and as more energy is required to overcome the electrostatic forces present, they have higher melting and boiling points.
explain the difference between primary, secondary and tertiary alcohols.
primary: carbon with -OH is bonded to one other carbon.
secondary: carbon with -OH is bonded to two other carbons
tertiary: carbon with -OH is bonded to three other carbons.
describe how primary and secondary alcohols can be distinguished from tertiary alcohols using acidified potassium dichromate.
when primary and secondary alcohols are added to acidified potassium dichromate, the solution will observe a colour change from orange to green. however, when a tertiary alcohol is placed in a solution of acidified potassium dichromate it will not under go any colour change.
oxidation of primary alcohols
mild oxidation results in the creation of an aldehyde, severe oxidation results in the creation of a carboxylic acid.
oxidation of secondary alcohols
oxidations results in the creation of a ketone.
oxidation of tertiary alcohols
when tertiary alcohols undergo oxidation they will not experience any change.
