Reactions of alkenes and alcohols (7.2) Flashcards
What are alkenes?
hydrocarbons with a double carbon-carbon bond
What is the general formula for the homologous series of alkenes?
CnH2n
Are alkene molecules saturated or unsaturated?
unsaturated
Why are alkene molecules unsaturated?
they have a double bond between the carbon atoms
What are the first four members of the homologous series of alkenes?
ethene, propene, butene and pentene
no ‘methene’ as it would not have a double bond due to only having one carbon atom
What forms can alkenes be represented in? (formula and diagram) e.g. for propene
What is the functional group of alkenes?
C=C
What determines the reactions of organic compounds?
the generality of reactions of functional groups
How do alkenes react with oxygen in combustion?
Alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons, but they tend to burn in air with smoky flames because of incomplete combustion
What is incomplete combustion caused by?
A lack of oxygen
How do alkenes react with hydrogen, oxygen and the halogens?
By the addition of atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond (double bond breaks) forming a saturated molecule
these are called addition reactions
What is the functional group of alcohols?
-OH
What are the first four members of a homologous series of alcohols?
methanol, ethanol, propanol and butanol
What forms can alcohols be represented in?
You can combine the formula if you want. e.g. for ethanol C2H5OH
or add another CH2 every time starting with alcohol (methanol doesn’t;t have this)
What is the formula of the homologous series of alcohols?
CnH2n+1OH
3 needed
What are the uses of alcohols?
- solvents
- fuels
- ethanol is main alcohol in alcoholic drinks
What is formed when alcohols burn in air?
carbon dioxide and water
What is formed when alcohols react with sodium?
form solution of sodium alkoxide (C2H5ONa)
What happens when alcohol is added to water?
mix easily to produce a solution (dissolve easily)
as the alcohol molecule gets longer, its solubility decreases
How can alcohols be oxidised without combustion?
Through use of an oxidising agent, to produce a carboxylic acid
What is the equation for the fermentation of sugar using yeast?
glucose ⇢ ethanol + carbon dioxide
yeast as a catalyst
2 needed + 2 minor
What are the conditions are needed for the fermentation of sugar using yeast?
- anaerobic conditions
- warm (temperature, 25-35°C)
- sugars dissolved in water, and mixed with yeast
- an air lock to allow carbon dioxide out, while stopping air getting in
What is the functional group of carboxylic acids?
-COOH
What are the first four members of a homologous series of carboxylic acids?
methanoic acid, ethanoic acid, propanoic acid and butanoic acid
What forms can carboxylic acids be represented in? (formula and diagram)
What is the general formula for the homologous series of carboxylic acids?
Cn-1H2n-1COOH
What happens when carboxylic acids react with carbonates?
carbonates gently fizz in solutions carboxylic acids, releasing carbon dioxide gas
What happens when carboxylic acids dissolve in water?
they form acidic solutions with pH values less than 7
What happens when carboxylic acids react with alcohols?
they form esters
What is the word equation for the reaction of ethanoic acid and ethanol?
ethanol + ethanoic acid ⇢ ethyl ethanoate + water
Why are carboxylic acids weak acids?
Carboxylic acids are weak acids because they only partially ionise in solution.
Their solutions do not contain many hydrogen ions compared to a solution of a strong acid at the same concentration
What are 2 properties of esters?
- volatile
- pleasant smell
so used in perfumes
What is the functional group of esters?
How are carboxylic acids produced?
The (oxidation) reaction between an alcohol and oxygen without combsution, using an oxidising agent
The oxidation of alcohols forms which products with and without combustion?
with combustion - carbon dioxide + water
without combustion - carboxylic acids
Incomplete combustion produces carbon monoxide or carbon particulates, due to a lack of oxygen, what is the problem with these two waste products?
Carbon monoxide - is a toxic gas
Carbon particulates - cause global dimming
Alkanes can be used as (…)
fuels
What is seen when fermentation takes place?
fizzing
What gas is produced when sodium reacts with ethanol?
hydrogen gas
What is the catalyst in a reaction between ethanol and ethanoic acid?
a strong acid
What is the compound added to ethene to produce ethanol?
Water
What is a test for carboxylic acids?
Add hydrogen carbonate
If carboxylic acid present, the solution will effervesce
- as dilute acid - for alcohol + other non-acids, this will not occur*
- could also use any metal or other carbonate, but it must be named*
What process is used to separate ethanol from water and what physical property allows this to occur?
fractional distillation
Both compounds have different boiling points (ethanol has lower boiling point than water)
3 needed
Which substances can be added to alkenes in an addition reaction?
- Halogens
- Water
- Hydrogen
How can different forms of poly(ethene) be produced from ethene?
Use different reaction conditions
