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chem
Alcohol, haloalkanes, and analysis
| Question | Answer |
|---|---|
| Polarity of alcohols | Contain O-H bonds which have differing electronegativities and so is polar Capable of forming H bonds |
| Volatility and boiling points of alcohols compared to alkanes | More energy required to break hydrogen bonds, higher boiling points and lower volatility than alkanes |
| Alcohols solubility in water | Polar O-H bond means alcohols are soluble as they form H bonds with water As chain length increases, solubility decreases as influence of -OH group diminishes |
| Alcohols classification | Primary: -OH attached to C attached to 1 alkyl group and 2H (includes methanol) Secondary: -OH attached to C attached to 2 alkyl groups and 1H Tertiary: -OH attached to C attached to 3 alkyl groups |
| Combustion of alcohols | Burn completely with O2 to form H2O and CO2 |
| Oxidation of alcohols | Oxidised by an oxidising agent (e.g K2Cr2O7/H2SO4) Primary: distillation to produce aldehydes (removes aldehyde preventing further oxidation), reflux to produce carboxylic acid Secondary: produces ketones Tertiary: does not oxidise H2O also a product |
| Elimination/dehydration of alcohols | Heated under reflux with acid catalyst (typically concentrated H3PO4) to remove H2O forming an alkene (H2O also product) |
| Substitution of alcohols | Alcohol, NaBr, and H2SO4 heated under reflux H2SO4 and NaBr react forming a HBr HBr reacts with alcohol to form haloalkane (H2O also a product) |
| Hydrolysis of haloalkanes | Aqueous OH- ions in alkalis substitutes the halogen, bond breaks by heterolytic fission forming an alcohol and halide ion With water, ethanol and silver nitrate you can investigate rate of hydrolysis by observing the colour of the AgX precipitate |
| Nucleophile | Electron pair donor |
| Rates of hydrolysis of haloalkanes | Bond enthalpies of the carbon-halogen decrease down the group, less energy required to break them meaning they hydrolyse at a faster rate |
| Impact of organohalides (e.g CFCs) | Photodissociation: CF2Cl2 --> CF2Cl• + Cl• Propagation: Cl• + O3 --> ClO• + O2 ClO• + O --> Cl• + O2 |
| Quickfit apparatus | Pear-shaped flask, receiver, screw cap adaptor, condenser, still head Used in reflux and distillation |
| Separating funnel | Separates organic and aqueous layers Water added to solution to observe which layer increases - this is the aqueous layer Acid impurities removed by adding aqueous sodium carbonate and stoppering the funnel to turn it and open the tap, releasing CO2 |
| Drying the product | Anhydrous salts (e.g calcium chloride) used to remove traces of water Water removed when drying agent stops clumping together |
| Redistillation | Removes organic impurities |
| Synthetic routes from alkanes | UV radiation --> haloalkanes |
| Synthetic routes from alkenes | H2 + Ni catalyst --> alkane Hydrogen halide/halogen --> haloalkane Steam + H3PO4 catalyst --> alcohols |
| Synthetic routes from alcohols | Any: Heated with conc H3PO4 --> alkene H2SO4 + NaBr --> haloalkane Primary: K2Cr2O7/H2SO4 --> aldehyde (distillation), carboxylic acid (reflux) Secondary: K2Cr2O7/H2SO4 --> ketone |
| Synthetic routes from haloalkanes | Reflux with aqueous NaOH --> alcohol |
| Infrared spectroscopy | Covalent bonds can absorb infrared radiation and vibrate (stretch or bend) more and absorb energy Absorbed IR is observed to identify bonds in organic molecules |
| Infrared in the atmosphere | IR re-emitted from Earth's surface as longer-wavelength IR - absorbed and re-emitted by atmospheric gases - temperature increases |
| Uses of IR spectroscopy | Monitor gas pollutants e.g CO and NO2 from car emissions Detecting alcohol with breathalysers |
| Mass spectrometry |
Created by:
silver54331