ORGANIC REACTIONS Flashcards
What does unsaturated mean?
Two fewer hydrogen atoms than an alkane with the same number of carbon atoms. Has a double carbon bond.
What is a functional group?
Part of the molecule that determines how it reacts eg a double bond in an alkene.
What is a homologous series?
Members of this series all have the same functional group.
How do alkenes burn?
With a smoky, yellower flame due to incomplete combustion. They also release less energy than alkanes, for this reason.
What is hydrogenation?
When alkenes react with hydrogen. A Nickle catalyst and 150 degrees Celsius is necessary.
Hydrogen is added across the double bond so the double bind is converted to a single bond. This produces an alkane.
What is hydration?
Reaction of an alkene with water. Makes an alcohol. 300 degrees Celsius Must be steam 70 atmospheres pressure Phosphoric avid catalyst Reversible.
How can ethanol be made?
The hydration of ethene.
High yield
Non renewable source
High temp/energy
OR Fermentation Anaerobic conditions Low temp/energy Renewable Makes an aqueous solution (ethanol dissolved in water) so need s to be purified through distillation which requires energy.
What are the products of methanol and sodium?
Sodium methoxide and hydrogen
What are the products of methanol and an oxidising agent?
Methanoic acid and water.
What are the products of ethanoic acid and sodium carbonate?
Sodium ethanoate and carbon dioxide and water.
What are the products of ethanoic acid and ethanol?
Ethyl ethanoate.
Requires sulphuric acid as a catalyst
What are the products of methanoic acid and magnesium?
Magnesium methanoate and hydrogen.
What are the products of propanoic acid and lead carbonate?
Lead propanoate and carbon dioxide.
What are the products of ethanoic acid and copper oxide?
Cooper ethanoate and water.
Why are alkenes more reactive than alkanes?
Because of their double bond. Molecules that react with alkene molecules ‘add’ to the alkene across their double bond.
How do you test for ethene?
Using bromine water. Ethene takes the orange colour out of the reaction mixture and leaves it colourless.
What happens when an alkene reacts with hydrogen?
The double bond in alkenes mean that they are unsaturated compounds, so their molecules do not contain the maximum number of hydrogen atoms possible.
By the addition of a hydrogen molecule across the double bond a saturated hydrocarbon, AN ALKANE, will be formed.
What conditions are needed for an alkene to react with hydrogen to form an alkane?
60 degrees celcius and the presence of a nickle catalyst.
Why are alkenes reacted with hydrogen?
To straighten their molecules and increase their melting points. For example, the right amount of hydrogen is added to make a margarine that will spread easily straight from the fridge.
What happens when alkenes react with water?
Ethanol can be made from ethene gas. Ethene gas can react with steam to make ethanol.
What conditions are needed for alkenes to react with water?
The reaction requires energy to heat the gases and to generate a high pressure.
The reaction is reversible, so ethanol can break down back into ethene and steam. So, unreacted ethene and steam are recycled over the catalyst.
How is the organic structure of an alcohol molecule written?
Replace one of the -H from an alkane molecule and change it to an -OH.
What are the first four alcohols in the homogolous series?
Methanol
Ethanol
Propanol
Butanol
What is the functional group of carboxylic acids?
-COOH
What are the first four carboxylic acids in the homogolous series?
Methanoic acid
Ethanoic acid
Propanoic acid
Butanoic acid
Esters?
???
How is ethanol made?
Made by fermenting sugars from plant material with yeast and is becoming an important alternative fuel to petrol and diesel.
Ethanol made by fermentation is termed a biofuel.
Can also be made in the industry from reacting ethene and steam in the presence of a catalyst. However, this method uses up some of the diminishing supplies of crude oil, a non-renewable resource.
What are some uses of alcohols?
Solvents in products such as perfumes, aftershaves and mouthwashes.
What happens during the combustion of alcohols?
Very flammable. It burns with a ‘clean’ blue flame.
What happens when alcohols react with sodium?
The sodium effervesces (gives off bubbles of gas), producing hydrogen gas, and gets smaller and smaller as it forms a solution of sodium ethoxide in the ethanol.
The reaction isn’t a vigorous as the reaction observed between water and sodium.
What happens during the oxidation of alcohols?
Combustion is one way to oxidise an alcohol.
However, when you use chemical oxidising agents such as potassium dichromate, you get different products.
An alcohol is oxidised to a carboxylic acid when boiled with acidified potassium dichromatebsolution.
Ethanol can be oxidised to ethanoic acid if it is left oxposed to air. Microbes in the air produce ethanoic acid from ethanol.
What is ethanoic acid?
Vinegar.
What are some typical reactions of carboxylic acids?
Reaction with a metal carbonate forms a salt, water and carbon dioxide.
What practical can be done to test the properties of an ethanoic acid solution?
Take the pH of the solution
Add a little potassium carbonate to the acid
Add a small piece of magnesium ribbon to the acid.
Test the conductivity of the solution in a small beaker using a simple circuit of a cell, two carbon electrodes, and a bulb. Collect the gas given off the negative electrode in a test tube. Then test it with a lighted spill.
Why are carboxylic acids called weak acids?
Carbon dioxide gas is given off more slowly when a metal carbonate reacts with a carboxylic acid, as compared with hydrochloric acid of the same concentration. That is because carboxylic acids are weak acids as opposed to strong acids, such as sulfuric acid or hydrochloric acid.
Acids must dissolve in water before they show their acidic properties. That is because in water all acids ionise (split p).
