Alcohols Flashcards
Alcohol general formula
CnH2n+1OH
Describe the shape of an alcohol
O 90° from C
H 104.5° from O
Alcohol physical properties
OH leads to hydrogen bonding
Higher mp/bp than alkanes
Short chain alcohols, soluble in water (H bond between alcohol and water molecules)
4 reasons alcohols are industrially important
Intermediates
Easily made
Easily converted to other compounds
Ethanol
What 3 main compounds can alcohols be converted into
Aldehydes
Ketones
Carboxylic acids
What is ethanol used for
Cosmetic solvent
Drug manufacture
Alcoholic drink manufacture
Describe the hydration of alkenes
Steam added across double bond
Forms an alcohol
Advantages and disadvantages of hydration of alkenes
A: fast, pure product, 95% yield, continuous
D: uses finite crude oil source, high energy cost (temp/pressure), high tech equipment
Describe fermentation of glucose
Forms ethanol and carbon dioxide
Carbs —> sugar cane/beet
Yeast enzymes
Anaerobic respiration
Advantages and disadvantages of fermentation of glucose
A: renewable source
D: carbon dioxide, greenhouse gas, global warming, slow, impure, fractional distillation needed, sugar cane takes up land for crops, high labour cost
Halogenation
Addition of a halogen to an alcohol
Conditions for hydration of alkenes (3)
300°C
60atm
solid phosphoric (V) acid catalyst
Conditions for fermentation of glucose (4)
30-40°C
yeast
air kept out, prevent oxidation —> ethanoic acid
15% alcohol enzymes don’t function, fractional distillation, increase alcohol content
Primary and secondary alcohol chlorination
Reactant: Anhydrous phosphorus (V) chloride, white solid
Conditions: Rigorous at rtp, no heating needed
Products: Makes choloralkane, phosphorus chloride, hydrogen chloride (white smoke)
Notes: Separate products via fractional distillation
Tertiary chlorination
Reactant: HCl
Conditions: Concentrated HCl, shake, rtp
Products: tertiary chloroalkane, water
Notes: ?
Bromination of alcohols
Reactant: KBr
Conditions: 50% concentrated H2SO4, warm
Products: Bromoalkane, water
Iodination of alcohols
Reactants: Red phosphorus, iodine —> phosphorus triiodide
Conditions: heat under reflux
Products: iodoalkane, phosphoric acid (H3PO3)
Dehydration of alcohols
Reactant: alcohol
Conditions: excess concentrated phosphoric acid, hot (170°C)
Products: alkene, water (removed from alcohol)
Notes: renewable alkene/polymer source, hydrogen that joins with OH to make water always taken from carbon adjacent to functional group
Dehydration of alcohols mechanism description
O electron pair to lone H+
C-O to positive O
Adjacent H-C to C+
Double bond forms and H+
3 types of oxidation
Complete
Incomplete
Sophisticated
What do each characterisation of alcohols oxidise to form
Primary: aldehyde then carboxylic acid
Secondary: ketones
Tertiary: don’t oxidise
Describe the oxidation of a primary alcohol
Reactant: alcohol
Conditions: potassium dichromate catalyst acidified with dilute H2SO4
Products: aldehyde (COH) then carboxylic acid (COOH)
Notes: dichromate ion reduced orange —> green, use H2SO4 not HCl otherwise acid is oxidised not alcohol
Describe the oxidation of a secondary alcohol
Reactants: alcohol
Conditions: dilute H2SO4 acidified potassium dichromate
Products: ketone (CO)
Notes: orange potassium chromate ions —> green
Describe the oxidation of a tertiary alcohol
Doesn’t occur
Would need to break a C-C not a C-H, stronger
Ketones/carboxylic acids don’t oxidise further
Can be oxidised via combustion
What is the purpose of distillation
Separate substances with different boiling points
Purify a product (chlorination tertiary alcohol, collect at desired bp)
Stop a reaction at a certain point (aldehyde from oxidise primary alcohol)
Distillation process (6)
Gently heat reaction mixture
Substances evaporate in ascending bp
Thermometer shows bp
Substances condense in condenser
Collect in conical flask
Anti bumping granules make boiling smoother
Why use a reflux reaction
Stop flammable/volatile product loss
Time to react fully
Reflux process (4)
Vertical Liebig condenser, everything evaporates
Drop back into reaction mixture/condense, keeps reacting
Heating usually electrical, water bath, hot plate (flammable product/reactants)
Anti bumping granules make boiling smoother
Ways of removing impurities
Insoluble in water: separation to remove impurities that do dissolve
Use other solvents as long as desired product doesn’t dissolve in it
Or add solvent it does dissolve in then remove via distillation
Removing impurities process (4)
Mixture in separating funnel, add solvent
Invert a few times, leave to settle, 2 layers form
Remove stopper, open tap, drain lower layer
Pour upper layer into separate flask
Washing use, process and example
Remove left over reagents/unwanted side products
Add liquid and shake
Organic liquid + organic acid, add sodium hydrogen carbonate, reacts with acid to form salt, acid is catalyst, carbon dioxide made
Drying process
Anhydrous salt
Bind to water, become hydrated
First go lumpy, add more till it looks like a snow globe
Drying agent removed via filtration
2 anhydrous salts good for drying
Magnesium sulphate
Sodium sulphate
Calcium chloride
