4.2.1 alcohols
- Created by: avocado05
- Created on: 06-03-22 19:05
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- Alcohols
- hydrogen bonds
- alcohols polar due to electronegative OH groups which pulls electrons in C-OH bond away from C
- oxygen in OH group draws elec. density away from hydrogen, giving it slight +ve charge
- +ve charge attract lone pairs on oxygen of another molecule forming H-bonds
- properties
- soluble in water
- H-bonds form between OH and H2O
- as alcohols inc. in size, solubility dec.
- in larger alcohols, C-chain has more influence (non-polar)
- this means less attraction for H2O molecules as C-chain uses london dispersion forces to dissolve
- less H-bonds
- this means less attraction for H2O molecules as C-chain uses london dispersion forces to dissolve
- in larger alcohols, C-chain has more influence (non-polar)
- low volatility (don't evap. easily)
- have higher boiling points than alkanes
- H-bond is strongest type of intermolecular force
- requires more energy to break
- bp inc as carbon chain inc.
- more electrons so more/stronger london dispersion forces
- requires more energy to break
- more electrons so more/stronger london dispersion forces
- alkanes only have london dispersion forces
- H-bond is strongest type of intermolecular force
- have higher boiling points than alkanes
- soluble in water
- oxidation
- primary alcohols
- partial oxidation = aldehyde
- oxidising agent = acidified potassium dichromate (K2Cr2O7)
- forms aldehyde which has lower bp than alcohol so distilled
- gentle heating and distilled with K2Cr2O7
- full oxidation = carboxylic acid
- stronger heating with excess acidified potassium dichromate
- reflux with K2Cr2O7
- partial oxidation = aldehyde
- secondary alcohols
- forms ketones when heated with acidified potassium dichromate
- doesn't need to be distilled as ketone cannot be further oxidised
- reflux with K2Cr2O7
- tertiary alcohols
- cannot be oxidised
- not enough hydrogens attached to carbon that carries OH group
- cannot be oxidised
- primary alcohols
- hydrogen bonds
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