Chemistry 7.2 (Alcohols, Carboxylic Acids and Esters)

Made up only of carbons and hydrogens

Carbon can be many different structures: simple molecular eg.carbon dioxide, giant lattice eg.graphite/diamond

Hydrocarbons are fuels 

(C_nH_2n+2)

Alkanes are hydrocarbons

Only has single C-C bonds, therefore alkanes are saturated compounds

Alkanes have covalent bonding therefore have strong intramolecular bonds, the larger the molecule to stronger the bonds (this makes them solids)

Properties: oily hydrocarbons don't mix with H₂O /aqueous solutions, flammable (products are H₂O and CO₂)

Functional group: C-H

eg. ethane C₂H₆

(C_nH_2n)

Contain a double C=C bond, they are unsaturated compounds which makes it more reactive than alkanes

Functional group: C=C

(C_nH_2n+1OH)

Short chains have low boiling points due to weak intermolecular forces (long chainshave higher boiling points), however this is still higher than the corresponding alkane because the O-H strengthens the intermolecular bonds; short chains are also soluble 

Flammable (products: carbon dioxide and water)

Functional group: O-H

Fermentation of sugar: C₆H₁₂O₆ --> 2C₂H₅OH + 2CO₂ ; glucose(maize/corn) --> impure ethanol + carbon dioxide. 

Advantages: low temperature/pressure, renewable resource, carbon neutral. Disadvantages: low atom economy (51%), impure ethanol, feedstock takes up land which could be used for housing and food 

Converting ethene: C₂H₄ + H₂O --> C₂H₅OH ; crude oil + water --> ethanol. 

Advantages: high atom economy (100%), 95% yeild, 96% pure ethanol. Disadvantages: high temperature/pressure, producing ethene requires energy, non-renewable source

Converting biomass: C₆H₁₂O₆ --> 2C₂H₅OH + 2CO₂ ; glucose(genetically modified e.coli bacteria) --> impure ethanol + carbon dioxide. 

Advantages: carbon neutral, renewable resource, low temperature/pressure. Disadvantages: low atom economy (51%), impure ethanol, fossil fuels need to purify

End in -COOH

Have unpleasant tastes and smells eg. rancid butter, sweaty socks, vinegar

eg. ethanoic acid CH₃COOH

Carboxylic acids are weak because they are organic acids, ie. with carbon, so only partially ionise when put in water

Inorganic acids, ie. without carbon, are strong as the they give off all of the hydrogen ions/fully ionise when put in water

Acid + Metal → Salt + Hydrogen

Acid + Alkali → Salt + Water (+ Carbon dioxide, if a carbonate)

Carboxylic Acid + Alcohol → Ester + Water

Carboxylic Acid + Alcohol → Ester + Water

Smells eg. pear drops (nice)

Used in fragrances, food, solvents etc

Making: heat alcohol and carboxylic acid under reflux with concentrated sulfuric acid (catalyst)

Reflux: heating under reflux prevents products escaping as they condense and fall back

Distillation: esters generally have lower boiling points than reactants

Purification: impurities dissolve in aqueous solution and then is tapped off

Drying: anhydrous (without water) calcium cholride absorbs water in organic ester layer which is then filtered off

Distillation: to remove impurities

Fats and oils are naturally occuring esters

Glycerol + fatty acids --> fats (alcohol + carboxylic acid --> ester + water),

They are long molecules and used as an energy store

Animal fats: solid, saturated (single bonds)- cannot add other atoms, bad for the heart

Vegetable fats (oil): unsaturated (double bonds)- able to snap open and introduce new atoms, healthier