Topic 5 - Organic Chermistry Flashcards
What is a homologous series?
A group of compounds with the same general formula so have the same elements & similar molecular formula, giving them similar chemical properties & react in a similar way
How do the physical properties of the homologous series change as they increase in size?
The boiling points increase as size increases (e.g. in fractional distillation)
What is the general formula for an alkane?
CnH2n+2
What is the formula for: methane? ethane? propane? butane?
CH4
C2H6
C3H8
C4H10
What is the difference between alkanes and alkenes?
Alkenes have at least one double bond in their chain of carbon atoms
What is the general formula for an alkene?
CnH2n
What is the formula for:
ethene?
propene?
butene?
C2H4
C3H6
C4H8
What is the general formula of an alcohol?
CnH2n+1OH
What is the formula for: methanol? ethanol? propanol? butanol?
CH3OH
C2H5OH
C3H7OH
C4H9OH
What is the functional group of an alcohol?
-OH
What is the functional groups of carboxylic acid?
-COOH
What is the general formula of carboxylic acid?
CnH2n+1COOH
What is the formula for: methanoic acid? ethanoic acid? propanoic acid? butanoic acid?
HCOOH
CH3COOH
C2H5COOH
C3H7COOH
What is the symbol equation for the fermentation of glucose?
C6H12O6 –yeast–> 2C2H5OH + 2CO2
How would you make a dilute solution of ethanol from glucose/other carbohydrates?
- Fermentation
- Mix yeast (contains an enzyme) + solution of a carbohydrate in clean container. Seal + leave in warm place
- Keep between 30 & 40˚C as temp than happens quicker (low = slower, fast = denaturing)
- Keep in anaerobic conditions as O2 converts ethanol to ethanoic acid
- When conc at 10-20% fermentation stops as yeast killed by alcohol
- Yeast falls to bottom, can collect ethanol from top
After the fermentation of carbohydrates into alcohol, how can the alcohol be made more concentrated?
Distilling
What is the process through which alcohol can be made more concentrated?
- Fractional distillation
- Ethanol has lower boiling point than water so when fermentation mixture is heated, ethanol evaporates + vapour rises up fractionating column, while water stays liquid
- Liebig condenser used to condense ethanol vapour by cooling it so concentrated ethanol can be collected in a separate flask
What are the advantages and disadvantages of fermentation?
+Uses renewable source so won’t run out
- Poor quality of ethanol
- So expensive to concentrate + purify ethanol
How is ethanol produced industrially?
- Ethene (C2H4) made by cracking crude oil fractions
- Ethene reacts with steam to make ethanol
What is the advantage of the industrial production of ethanol?
- Relatively cheap as ethane’s fairly cheap + not much wasted
- Made in large chemical plant so made continuously + quickly. Product = high quality + needs little further processing
What is the disadvantage of the industrial production of ethanol?
-Ethane’s produced from crude oil which isn’t renewable so ethanol will become v. expensive
What is the word equation for the reaction of ethene with water?
ethene + water (steam) –> ethanol
What effects does alcohol have on the body?
- Less inhibited so socialise + relax w/ each other
- Reduces activity of nervous system, increasing reaction times, impaired judgement, poor balance/coordination, unconsciousness, coma
- In excess = dehydration, damaging brain cells causing drop in brain function leading to long term memory loss. Also liver damage = liver disease
What effects does alcohol have on society?
- Loutish behaviour + violence
- Addiction, alcoholism, leading to family breakdowns, + alcoholics losing their jobs or becoming homeless
- Drunk = irresponsible sexual behaviour, increasing risk of catching STIs
- Drink driving = serious injury/death
- Economic costs: more people to deal w/ drunks
How is ethene formed from ethanol?
- Dehydration
- Ethanol vapour passed over hot aluminium oxide catalyst
What is the word and symbol equation for the dehydration of ethanol?
ethanol –> ethene + water
C2H5OH –> C2H4 + H2O
How is vinegar produced from ethanol?
- Wine/beer left open to air, ethanol is oxidised to ethanoic acid
- Ethanoic acid is the acid in vinegar
- Vinegar is used for preserving foods + flavourings
What is the word and symbol equation for the oxidation of ethanol?
ethanol + oxygen –> vinegar + water
CH3CH2OH + O2 –> CH3COOH + H2O
With ethanoic acid as an example, how to carboxylic acids react with metals?
ethanoic acid + magnesium –> hydrogen + magnesium ethanoate
2CH3COOH + Mg –> H2 + (CH3COO)2Mg
With ethanoic acid as an example, how to carboxylic acids react with bases?
ethanoic acid + sodium hydroxide –> sodium ethanoate + water
CH3COOH + NaOH –> CH3COONa + H2O
With ethanoic acid as an example, how to carboxylic acids react with carbonates?
ethanoic acid + sodium carbonate –> sodium ethanoate + carbon dioxide + water
2CH3COOH + Na2CO3 –> 2CH3COONa + CO2 + H2O
What effect does ethanoic acid (and all acids) have on universal indicator and blue litmus paper?
- Turns universal indicator orange/red
- Turns blue litmus paper red
What is the functional group of esters?
-COO-
When are esters formed?
When an alcohol reacts with a carboxylic acid (acid catalysts usually used e.g. concentrated sulphuric acid)
What is the word equation for the reaction between an alcohol and a carboxylic acid?
alcohol + carboxylic acid –> ester + water
What is the word and symbol equation for the production of the ester ethyl ethanoate?
ethanoic acid + ethanol –> ethyl ethanoate + water
CH3COOH + C2H5OH –> CH3COOC2H5 + H2O
What are esters used for?
-Perfumes
-Used to make flavourings + aromas
(-Often smell sweet + fruity)
What is a polyester?
Polymers (long chain molecules) which contain the ester functional group
What can polyester be used for?
- Plastic bottles
- Polyester fibres can be made into fabric e.g. to make clothes, lighter/cheaper to use than some traditional materials e.g. wool
- Can be recycled + turned into fleece to make clothing
How are soaps formed?
When an ester reacts with an alkali
How can fats and oils be made into soap?
- Fats or oils are a type of ester
- Can be boiled up w/ concentrated alkali solution to make soap
- Oil/fat breaks down into glycerol + long chain carboxylic acids + the carboxylic acids go on to react with the alkali
What does hydrophobic mean and what part of the soap anion is this usually?
Doesn’t like water but attracted to grease. Normally the long hydrocarbon chain or ‘tail’ of the molecule
What does hydrophilic mean and what part of the soap anion is this usually?
Dissolves in water (+ not oil + fat). Normally small + ionic, the ‘head’
What do soap anions do?
- Let water + oil mix
- Soap anions surround the oil + form droplets
- e.g. this is how washing soap helps lift oily stains out of fabric
What does unsaturated mean?
At least on C=C double bond
How does the texture of unsaturated oils compare to that of saturated oils?
-Unsaturated = less viscous
How can liquid unsaturated oils be changed to solid unsaturated oils?
- By breaking the double bonds + adding hydrogen
- Nickel catalyst used to help reaction, w/ high temp, pressure
- Called catalytic hydrogenation
- Nickel catalyst is solid + can be filtered out again
- As filtered oil cools down to room temp, turns into a solid fat
What are polyunsaturated vegetable oils used for?
To make margarine through hydrogenation
