Ch.15 - Organic Compounds Flashcards
What are saturated and unsaturated organic compounds?
Saturated chemical compounds only contain single bonds. In saturated organic compounds, all carbon atoms are tetrahedral.
Unsaturated chemical compounds contain a double or triple bond.
What are aromatic and aliphatic compounds?
Aromatic compounds contain a benzene ring. Aliphatic compounds don’t have a benzene ring.
What are alkanes? Give the general formula for alkanes.
Alkanes form a homologous series of aliphatic hydrocarbons. They are saturated compounds. They are non-polar. CnH2n+2
What are alkenes? Give their general formula. What causes their increasing boiling point?
Alkenes form a homologous series of aliphatic hydrocarbons. They are unsaturated compounds, containing a non-polar carbon=carbon double bond. CnH2n. Van der Waals’ forces increases the boiling point of hydrocarbons as the number of carbons increases. They are either non-polar or slightly polar. Low solubility in water, high solubility in non-polar substances.
What are hydrocarbons?
Hydrocarbons are compounds of carbon and hydrogen only which are covalently bonded.
What is a planar carbon compound?
A planar carbon compounds have a C=C or C=O double bonds.
What are mercaptans?
Mercaptans are added to natural gases. They have a strong smell (usually of S) to alert for leaks.
What are structural isomers?
Structural isomers are compounds that have the same molecular formula but different structural formulae.
What causes alkanes increasing boiling points? Name the states of the alkanes.
Alkanes with longer C chains have stronger van Der Waals’ forces between molecules. The attraction requires more energy to break apart. Methane to butane are gases. Pentane and above are liquids at room temperature. More than 15 carbons gives a waxy liquid alkane.
Name non-polar substances.
Cyclohexane and methylbenzene.
What are alkynes?
Alkynes form a homologous series of aliphatic hydrocarbons. CnH2n-2. Suffix: -yne
Each alkyne contains a carbon triple bond. Alkynes are unsaturated. They are non-polar. Lower alkynes are gases while higher alkynes are liquids or solids at room temperature. Methyne is non-existant.
What is auto-ignition?
Auto-ignition is ignition in an internal combustion engine before a spark is produced by the spark plug.
What is an octane number?
An octane number is a measure of the tendency of a fuel to resist auto-ignition.
What is the fractional distillation of crude oil(fractionation)?
Fractional distillation is the separation of crude oil, using distillation, into components according to their boiling points.
Draw the diagram for fractional distillation.
How does auto-ignition(knocking) occur?
Auto-ignition occurs when the reaction between petrol and air happens too soon due to increased pressure in the engine and low octane fuels. The petrol and oxygen should explode as a result of the spark plug.
What influences the octane number of hydrocarbons?
In straight-chained hydrocarbons, the shorter the alkane, the higher the octane number(isomerisation). In branched-chained hydrocarbons, the greater the number of branches, the higher the octane number. Cyclic and aromatic hydrocarbons have a higher octane number(dehydrocyclisation). The addition of oxygenates.
What is the octane number of 2,2,4-trimethylpentane and heptane.
2,2,4-trimethylpentane has an octane number of 100, while heptane has one of 0.
What is catalytic cracking?
Catalytic cracking is the splitting of long-chain hydrocarbons into smaller molecules using heat and catalysts.
What are the advantages of catalytic cracking?
Long-chain compounds are converted into more useful compounds. Branched chain alkanes with shorter chain lengths are formed that have high octane numbers and are used for making petrol. Alkenes are formed, which are the starting compounds for the manufacture of polymers.
What is hydrogen used for?
Hydrogen is used for manufacturing ammonia, hydrogenation of vegetable oils to make margarine and manufacturing HCl.
How is hydrogen produced on a large scale?
Hydrogen may be produced on a large scale by steam reforming of natural gas or by electrolysis of water.
What is refinery gas?
Refinery gas is the fraction with the lowest boiling point. It is sold for domestic use. Propane and butane can be liquified from this fraction under pressure, it is called LPG(liquid petroleum gas).
What is light gasoline and naptha?
Light gasoline is used to make petrol. Naphtha is used to make raw material for the petrochemical industry.
Mandatory experiment:
Preparation of ethyne.
-Give formula and diagram
-What type of reaction is involved?
-Give method
-Describe appearance of CaC2
-Why is copper sulphate solution used?
-Why is the first tube discarded?(SH)
Set up apparatus like diagram. Place water into the flask dropwise. Collect the gas in test tubes and stopper each gas-filled tube underwater.
This addition reaction is exothermic.
CaC2 is a grey solid.
The copper sulphate solution removes impurities such as hydrogen sulphide and phosphine.
The 1st tube is discarded as it could form an explosive mixture.
Mandatory experiment:
Preparation of ethene
-Give formula, with the structural formulae and diagram
-What type of reaction is involved?
-Give method
-Describe appearance of Al2O3
-Give one measure of safety
-Why is the first tube discarded?(SH)
This is an elimination reaction. It is an example of heterogeneous catalysis.
Ethanol is put in first, then glass wool to soak it up. The boiling tube is placed horizontally. The Al2O3 is heated.
Al2O3 is a white powder.
Avoid ‘suck-back’ by removing cork before the flame is turned off after the experiment. H2O not Ca(OH)2 in formula.
Mandatory experiment:
Melting point determination of benzoic acid.
-method
-diagram
Take a small sample of benzoic acid. Heat on aluminium block with thermometer in it. Note the temperature the samples melt at.
The pure sample melts at a sharp temperature while the impure sample melts over a wide range of temperatures. The impure sample melts at a lower temperature than the pure sample.
Mandatory experiment:
The extraction of eugenol from clove by steam distillation.
-method
-diagram
-safety precautions
Place the cloves in a pear shaped flask. Place water in the steam generator, connect and boil. Use anti-bumping granules in the steam generator. After 30 minutes, disconnect the steam generator to avoid suckback, then turn off the heat. Collect 50cm^3 of pale milky distillate(emulsion). Note smell.
Have a safety opening on the boiling flask to prevent a build-up of pressure. If the level of water is too low, the system will not work well. Remove heat, carefully loosen safety valve and top-up the flask with water. Reconnect everything and heat again.
