Organic Chem Flashcards
Prefixes
Met- : 1 Eth- : 2 Prop-: 3 But-: 4 (optional) Pent-: 5 Hex-: 6
What are Hydrocarbons?
Organic compounds that contain hydrogen and carbon are called hydrocarbon
Alkane general properties
Saturated hydrocarbons
single covalent bond between carbon atoms
general formula: Cn H2n+2
Structural formula:
CH3, CH2 … CH2, CH3
Differs from next member by CH2(Mr:14)
Isomers
Isomers are compounds that have the same molecular formula but different structural formula are called isomers.
Alkane/Alkene Physical properties
Melting and boiling points ↑ as no. carbon atoms ↑ , molecular size ↑, stronger intermolecular forces of attraction
Viscosity ↑ as no. carbon atoms ↑, length of carbon chains ↑, ↑molecular size, ↑ intermolecular forces of attraction, thus ↑ difficulty of liquid to flow
Flammability ↓ as no. carbon atoms ↑, ↑ in percentage of carbon atoms present, thus making it harder to burn due to ↑amount of oxygern required, ↑ chance of incomplete combustion, producing smokey flame w soot
Alkane Chemical properties: Combustion (common reaction)
alkane + excess oxygen → CO2(g) + H2O(g)
eg: CH4 + 2(O2) → CO2(g) + 2(H2O) (g)
Incomplete combustion:
eg: 2CH4 + 2(O2) → 2CO(g) + 4H2O(g)
Fractional Distillation of Crude Oil
Order:
fraction - uses - boiling range
Petrolium - fuel for cooking and heating- ↓40
Petrol - fuel for cars - 40-75
Naphtha - making chemicals(plastic detergents)-90-150
Kerosene - Fuel for aircrafts, cooking&heating - 150-240
Diesel - fuel for diesel engines - 220-250
Lubricating oil- lubricating machines, wax -300-350
Bitumen - making roads, roofing - 350↑
Pretty Princesses Never Kiss Dirty Little Boys
as ↓, no of carbon ↑
as ↓, no boiling point ↓
Properties of isomers
Lower melting point and boiling point → due to smaller surface area → weaker intermolecular forces of attraction → less intermolecular forces of attraction
weaker intermolecular forces of attraction thus less energy required to overcome it
Alkene General properties
Unsaturated hydrocabons
contains carbon double bonds
CnHn where n>2
differs from next member by CH2 (Mr:14)
CH2, CH, CH2……CH2, CH3
Alkene Chemical properties: Combustion (common reaction)
alkene + excess oxygen → 2CO2(g) + 2H2O(g)
eg: C2H4 + 3(O2) → 2CO2(g) + 2(H2O) (g)
Incomplete combustion:
eg: C2H4 +2 (O2) → 2CO(g) + 2H2O(g)
Alkane chemical properties: Substitution reaction (signature reaction)
requires Uv light as catalyst
alkene + chlorine/bromine → chloro/bromo(alkane) + hydrochloric acid
eg: CH4 + Cl2 → CH3Cl + HCL
CH3Cl + CLS → CH2CL2 + HCL
Alkane chemical properties: Substitution reaction (signature reaction)
requires Uv light as catalyst
alkene + chlorine/bromine → chloro/bromo(alkane) + hydrochloric acid
eg: CH4 + Cl2 → CH3Cl + HCL
CH3Cl + CLS → CH2CL2 + HCL
Alkane chemical properties: Cracking ( crossover reacction )
Requires Aluminiun oxide/Silicon dioxide as catalyst, temperature of 600°C
alkane → alkenes + hydrogen gas
alkane → alkenes + alkenas
eg: C2H6 → C2H4 + H2
C3H8 → CH4 + C2H4Alkene Chemical properties: Hydrogenation
Requires 200 °C + nickel catalyst
Alkene + hydrogen → Alkane
eg: C2H + H2 → C2h44
used to turn unsaturated vegtable oils to margerrine
Alkene Chemical properties: Bromination (signature reaction)
from reddish brown(concentrated)/yellow(diluted) → colourless
alkene + bromine → Bromoethene
eg: C2H4 + Br2 → C2H4Br2
Alkene Chemical properties: Hydration (crossover)
300°C + 60atm (pressure) + phosphoric acid catalyst
alkene + steam → alcohol
eg:C2H2 + H2O → C2H3OH
Alkene chemical properties :Polymerisation
requires high pressure (1000atm) + 200°C + titanium(III) chloride/ Chromium (VI) oxide
Alkene + alkene → poly ethene
eg: C2H4 + C2H4 → C4H8
used to make plastics: polyethene
Alkene chemical properties: Addition reaction (signature reaction):
CH2CH2 + XY → CH2XCH2Y
Alcohol general properties
Not a hydrocarbon
General formula: CnH2n+1OH
differs from previous member by CH2(Mr:14)
CH3,CH2,CH2….OH
Alcohol Physical properties
soluble in water: Solubility ↓ as carbon ↑: meth,eth,prop can dissolve readily
Melting and boiling point ↑ as molecular size ↑ as molecular forces of attraction ↑ ( but have a lower boiling and melting point)
Flammability ↓ as the molecular size increases due to ↑ % of carbon
Alcohol Chemical Properties: Combustion (common reaction)
Complete combustion:
Alcohol + Oxygen → Carbon dioxide + Water
eg: C2H5OH + 3O2 → 2CO2 + 3H2O
Incomplete combustion:
Alcohol + oxygen → carbon monoxide + water
Alcohol Chemical properties: Oxidation ( signature reaction)/(crossover reaction)
Alcohol + oxygen from KMnO4 → Carboxylic acid + water
(oxygen from air too but it takes significantly longer)
eg: C2H5OH(aq) + 2[O] → CH3COOH(aq) + H2O(l)
Alcohol Chemical properties: Fermentation (manufacturing)
Conditions required: an anaerobic ( without oxygen), yeast and temp of 37°C ( inactive <18 and denatured>40 )
takes a few days
Glucose solution →(yeast)→ Ethanol + Carbon dioxide
C6H12O6(aq) →(yeast)→ 2C2H5OH(aq) + 2CO2(g)
Reaction:
The yeast is a MICROORGANISM that contains ENZYMES which break down GLUCOSE to form ETHANOL and CARBON DIOXIDE. The alcohol produced is only 20% as yeast is denatured when alcohol is too concentrated. Test for CO2 using LIMEWATER
Uses of Alcohol (ethanol)
Alcohol is used to make alcoholic drinks
it is a good solvent for organic compounds+ dissolves solutes that cant be dissolved in water
Used as a solvent for paints, varnishes, deodorants, perfumes, colognes and after-shaves lotions
Volatile (evaporates quickly)
used as fuel and(methylated spirit)→spirit lamps and cookers
make vineger
