chemistry - alcohols

IGCSE Edexcel Alcohols (organic chemistry) flashcards

what is meant by functional group?

a group of atoms that determine the chemical reactions of a homologous series

what is meant by homologous series?

a series of compounds with the same functional group, general formula, similar chemical properties and trends in physical properties

what is the functional group of alcohols?

• hydroxyl - all end in -ol

• -OH

what is the general formula for alcohols?

C_nH_2n+1OH (separate to show fg), or C_nH_2n+2O

name the first four alcohols

• methanol

• ethanol

• propan-1-ol

• butan-1-ol

give the molecular formula of methanol

CH₃OH (H₄O)

give the molecular formula of ethanol

C₂H₅OH (H₆O)

give the molecular formula of propan-1-ol

C₃H₇OH (H8O)

give the molecular formula of butan-1-ol

C₄H₉OH (H₁₀O)

give the structural formula of methanol

CH₃OH

give the structural formula of ethanol

CH₃CH₂OH

give the structural formula of propan-1-ol

CH₃CH₂CH₂OH

give the structural formula of butan-1-ol

CH₃CH₂CH₂CH₂OH

what is the displayed formula of methanol?

what is the displayed formula of ethanol?

what is the displayed formula of propan-1-ol?

what is the displayed formula of butan-1-ol?

what is the word equation for the complete combustion of ethanol?

ethanol + oxygen → carbon dioxide + water

what is the chemical equation for the complete combustion of ethanol?

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

what are the two possible word equations for the incomplete combustion of ethanol?

ethanol + oxygen → carbon + water

ethanol + oxygen → carbon monoxide + water

what are the two possible chemical equations for the incomplete combustion of ethanol?

C₂H₅OH + O₂ → 2C + 3H₂O

C₂H₅OH + 2O₂ → 2CO + 3H₂O

what is produced when an alcohol is oxidised?

carboxylic acid + water

what are the two kinds of oxidation of ethanol?

• microbial

• chemical

what is the word equation for the microbial oxidation of ethanol?

ethanol + oxygen → ethanoic acid + water

what oxidising agent is required for microbial oxidation of ethanol?

bacteria (above arrow)

what is the chemical equation for the microbial oxidation of ethanol?

C₂H₅OH + 2[O] → C₂H₃OOH + H₂O

what is the word equation for the chemical oxidation of ethanol?

ethanol + oxygen → ethanoic acid + water

what conditions are needed for the chemical oxidation of ethanol?

• presence of potassium dichromate (IV) (K₂Cr₂O₇)

• presence of dilute sulfuric acid

• heat

what colour change is seen when ethanol is oxidised during chemical oxidation?

orange → green

what is the chemical equation for the chemical oxidation of ethanol?

C₂H₅OH + 2[O] → C₂H₃OOH + H₂O

what two processes are there for the production of ethanol?

• hydration

• fermentation

what is the word equation for fermentation?

glucose (aq) → ethanol + carbon dioxide

what is the chemical equation for fermentation?

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

what conditions are required for fermentation?

• anaerobic

• yeast - catalyst

• 30^OC

why are anaerobic conditions required for fermentation?

so that the yeast respires anaerobically to produce ethanol otherwise ethanol would not be produced if oxygen was present

why is a temperature of 30C required for fermentation?

• not too high so enzymes don’t denature and the reaction stops happening (slows)

• not too low so the rate of reaction is high enough

what can be used as a source of glucose?

sugar cane

what is the word equation for hydration?

ethene (g) + water (g) → ethanol (g)

what is the chemical equation for hydration?

C₂H₄ + H₂O → C₂H₅OH

what conditions are required for hydration?

• 300C

• 65 atm (pressure)

• phosphoric acid catalyst (H₃PO₄)

is hydration a reversible reaction?

yes

what type of resources does fermentation use?

renewable, cheap resources

what type of resources does hydration use?

finite, non-renewable resources

what type of process is fermentation?

batch process - inefficient - takes a long time

what type of process is hydration?

continuous process - more efficient

what is the quality of product like for fermentation?

impure - contains CO₂ - needs distillation as it is unconcentrated and purification

what is the quality of product like for hydration?

pure

what is the rate of reaction for fermentation?

slow - days

what is the rate of reaction for hydration?

fast

what is the energy usage like for fermentation?

low - needs low temperature and low pressurer

what is the energy usage like for hydration?

high and thus also expensive - needs extremely high temp and pressure

what is the atom economy for fermentation?

makes by product

what is the atom economy for hydration?

makes only desired product