Organic Chemistry

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How does infrared radiation affect covalent molecules?
It causes the covalent bonds to vibrate as they absorb more energy.
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Which bonds are affected by IR radiation in greenhouses gases, CO2, H2O and CH4, and what is the effect on the environment?
C=O, O-H and C-H. By releasing more green houses gases into the environment means more IR can be absorbed leading to artificial warming of the planet.
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What do the O-H and C=O peaks represent?
O-H peak represents an alcohol, a narrow C=O peak represents a aldehyde or a ketone and. Broad C=O peak represents a carboxylic acid.
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What are the uses of IR spectroscopy?
Monitor gases causing air pollution from car engines and modern breathalysers to measure ethanol in breath.
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What is the molecular ion peak in mass spectroscopy?
The molecular mass of the molecule minus one.
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How do you work out the structure of a molecule in mass spectroscopy?
Fragmentation of the peaks.
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Why do you sometimes get a M+1 peak?
Due to a small amount of carbon-13.
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What is a primary, secondary and tertiary alcohol?
A primary alcohol has one alkyl chain, r, a secondary alcohol has two alkyl chains and tertiary has three alkyl chains.
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Describe the MPT/BPT of alcohols.
Increasing the chain length increases the MPT/BPT, higher than the equivalent alkanes due to formation of H bonds.
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Describe the volatility of alcohols.
H bonds make alcohols less volatile - smaller alcohols are more volatile than bigger ones.
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Describe the solubility of alcohols.
Dissolve in water due to the H bonds formation. Large alcohols are insoluble because they become more non-polar.
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Describe the combustion of alcohols.
Produces CO2 and H2O with a high enthalpy value. Can be a form of renewable energy if from sugar cane (no sulfur so less acid rain).
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Describe the dehydration of alcohols.
Heat with reflux for 40 minutes with a phosphoric acid catalyst to produce an alkene.
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Describe halide substitution in alcohols.
Halide replaces the OH group to form a haloalkane. HBr is made in situ by reacting NaBr with H2SO4.
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Describe distillation.
A quick fit apparatus method to separate miscible liquids due to different BPT. Using a round bottom flask, a heating mantle, a thermometer and it's holder, a condenser, a collecting flask and a clamp stand with its boss.
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Describe reflux.
A quick fit apparatus method to prevent the mixture from boiling away. Using a pear shaped flask, heating mantle and a condenser.
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How do you identify an unsaturated hydrocarbon?
Decoloursises bromine water.
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How do you identify a haloalkane?
Using silver nitrate, ethanol and water to produce white (chloro), cream (bromo) and yellow (iodo) precipitates.
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How do you identify a carbonyl?
With Cr2O7-, ketones no change and aldehydes orange to green. With Fehling's reagent, ketone no change and aldehyde dark red precipitate. With Tollens' reagent, ketones no silver mirror and aldehydes silver mirror.
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How do you identify a carboxylic acid?
Universal indicator - weak pH. Reactive metal - H2 effervescence. Metal carbonate - CO2 effervescence.
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How do you identify an alcohol?
Add carboxylic acid and H2SO4, produces ester smell.
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Define nucleophile.
An electron pair donor.
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Define nucleophilic substitution.
A chemical reaction in which an atom or group of atoms is exchanged for a nucleophile.
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How are halogen radicals produced?
By UV light on CFCs in upper atmosphere.
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Where were CFCs used?
In fire-fighting equipments and refrigerants because they are non-toxic.
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Describe oxidation of a primary alcohol.
Gentle heating with acidified potassium dischromate and aldehyde immediately distilled off. Stronger heating under reflux with excess Cr2O7- forms a carboxylic acid.
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Describe oxidation of a secondary alcohol.
Heating under reflux with Cr207- to form a ketone.
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Why can't tertiary alcohols be oxidised?
There are no available hydrogen atoms as singly bonded to carbon bonded to alcohol group, so no colour change.
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What colour change accompanies oxidation of alcohols?
Orange to green.
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Describe hydrolysis of haloalkanes.
Add ethanol as a solvent and AgNO3 for rate by water or use an aqueous alkali e.g. AgNO3 to test for coloured precipitate of AgX.
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Describe and explain the rate of hydrolysis of haloalkane.
Rate of hydrolysis increase from chloro to iodo because bond enthalpy increases which outweighs bond polarity.
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Define alkanes.
A saturated hydrocarbon containing single sigma bonds.
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Define sigma bonds.
The overlap of orbitals directly between the bonding atoms, which allows free rotation.
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Describe the shape around a carbon atom in an alkane.
Tetrahedral with bond angle 109.5 degrees.
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Describe the BPT of alkanes in terms of chain length.
Increase chain length, increase molecular mass, more SA contact between molecules, increased number of induced dipole-dipole interactions, so more energy needed to overcome intermolecular attraction so higher BPT.
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Describe the BPT of alkanes in terms of branching.
Increase branching, fewer SA interactions between molecules as they do not fit so closely together, fewer number of induced dipole-dipole interactions so lower BPT.
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Describe the reactivity of alkanes.
Low reactivity with many reagents because they have high bond enthalpies and C-H sigma bonds have a very low polarity as electronegativies are almost the same.
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What is the effect of CO when inhaled into lungs?
Toxic gas diffuses into blood and forms coordinate bond with haemoglobin, reducing its O2 carrying ability causing light headedness, faster breathing, unconsciousness and death.
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What is halogenation?
Homolytic fission of halogen to form radicals that can substitute a hydrogen atom in an alkane in the presence of UV light.
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What are the 3 stages of radical substitution?
Initiation - formation of radicals. Propagation - 2 repeated steps that build up a desired product in a side reaction. Termination - 2 radicals collide and make a stable product.
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What are the problems with radical substitution?
Its unpredictable because it is caused randomly by radicals colliding with another species allowing further substitution, so it's difficult to control. The mix of organic products has to be separated by the process of fractional distillation.
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Define alkenes.
Unsaturated hydrocarbons containing muntiple carbon-carbon bonds.
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Define a pie bond.
The sideways overlap of p-orbitals above and below the carbon atoms, which gives restricted rotation.
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Describe the shape around a carbon double bond in an alkene.
Trigonal planer, bond angle 120 degrees.
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Define stereoisomerism.
Compounds with the same structural formula but different arrangement of atoms in space.
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What is E/Z isomerism?
The carbon double bond has two different functional groups attached to each carbon atom. E - groups on opposite side. Z - groups on same side.
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What is cis-trans isomerism?
One of the attached groups to each carbon of the double bond is hydrogen. Trans - H on opposite side. Cis - H on same side.
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What is the Cahn-Ingold-Prelog priority rule?
Higher the atomic number, higher the priority.
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Why are alkenes more reactive than alkanes?
Pie bond has a lower enthalpy than sigma bond.
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Describe the addition of hydrogen to an alkene.
Add H2 at 150 degrees with a nickel catalyst.
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Describe the addition of bromine to an alkene.
Add Br2.
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Describe the addition of hydrogen halides to an alkene.
Add HBr.
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Describe the addition of steam to an alkene.
Add H2O(g) at 300 degrees and 65 ATM with a phosphoric acid catalyst.
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Define a electrophile.
An electron pair donor.
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Define electrophilic addition.
An electrophile is attracted to an electron rich centre or atom, where it accepts a pair of electrons to form a covalent bond.
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Under standard conditions a major and minor product results when hydrogen hakide is added to an unsymmetrical alkane. Which is the major product?
The most stable carbonation. Tertiary is the most stable because alkyl groups are electron releasing so push electrons towards the carbocation to reduce the positive charge.
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Other cards in this set

Card 2

Front

Which bonds are affected by IR radiation in greenhouses gases, CO2, H2O and CH4, and what is the effect on the environment?

Back

C=O, O-H and C-H. By releasing more green houses gases into the environment means more IR can be absorbed leading to artificial warming of the planet.

Card 3

Front

What do the O-H and C=O peaks represent?

Back

Preview of the front of card 3

Card 4

Front

What are the uses of IR spectroscopy?

Back

Preview of the front of card 4

Card 5

Front

What is the molecular ion peak in mass spectroscopy?

Back

Preview of the front of card 5
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