year 1

Are halogenoalkanes soluble in water?

No, they are insoluble as C-H bonds are non-polar, which is not compensated enough by C-X bond polarity.

Do halogenoalkanes have a polar bond?

Yes, they have a polar bond because halogens have a higher electronegativity than carbon, making the halogen δ- and carbon δ+.

Which intermolecular forces do halogenoalkanes have?

They have permanent dipole-dipole and van der Waals forces of attraction due to C-X bond polarity creating permanent dipoles.

How does the mass of a haloalkane compare with the mass of an alkane of the same chain length?

The mass of a haloalkane is greater than that of an alkane of the same chain length because the mass of halogen is greater than the mass of hydrogen.

What is the order of reactivity of halogenoalkanes?

Reactivity increases down the group despite C-F being the most polar bond; the bond enthalpy of C-X decreases down the group.

What is a nucleophile?

A nucleophile is a negatively charged ion or δ− atom that has a lone pair of electrons which can be donated to an electron-deficient atom.

What is nucleophilic substitution?

It is a reaction where a nucleophile donates a lone pair of electrons to a δ+ carbon atom, leading to the leaving of a δ− atom from the molecule.

What is the problem with CFCs?

CFCs, while unreactive under normal conditions, catalyse the breakdown of ozone in the atmosphere through free radical substitution.

What are the conditions/reactants needed for the elimination reaction of haloalkanes?

NaOH or KOH dissolved in ethanol with no water present, and the reaction needs to be heated.

How do you test for alkenes and what is the result?

Shake with bromine water; bromine water is decolorised from orange to colourless.

How do you test for haloalkanes? What is the result?

Add NaOH (aq), warm, acidify with HNO3, and add AgNO3(aq); result is precipitate of AgX (for Cl=white, for Br=cream, for I=yellow).

How do you test for alcohols? What is the result?

Add acidified K2Cr2O7 and heat; colour change from orange to green for 1° and 2° alcohols (no change for 3° alcohols).

How do you test for aldehydes? What are the results?

Warm with Fehling’s solution (brick red ppt forms from blue solution) or warm with Tollens’ reagent (silver mirror forms).

How do you test for carboxylic acids? What is the result?

Add Na2CO3(aq); result is CO2(g) given off - effervescence.

What is mass spectrometry and how does it work?

Used to find the relative molecular masses of organic compounds; involves dissolving the compound, ionising it, accelerating it, and reading the current at the detector to find m/z values.

What does the x-axis show on a mass spectrum?

It shows the m/z value (mass divided by ionic charge); effectively indicates the molecular weight (Mr), since most ions are 1+.

Why are there multiple peaks in a mass spectrum?

The molecular ion is shown as a peak, but it also fragments into smaller molecules, and different peaks may also result from isotopes of atoms.

How does gas chromatography work?

Gas chromatography uses a stream of gas to carry a mixture of vapours through a column packed with solids, separating compounds that move at different speeds.

What might GCMS be used for?

Forensic analysis, measuring water pollution, drug testing in athletes and racehorses.

What is high-resolution mass spectrometry?

Mass spectrometers that provide molecular mass to 3 or 4 decimal places.

What does high-resolution mass spectrometry allow you to do?

Distinguish between compounds with the same Mr to the nearest whole number but different atomic compositions.

Why do atoms absorb infrared radiation?

Atoms and chemical bonds absorb infrared radiation because they are constantly vibrating, absorbing frequencies matching their vibration.

How does infrared spectroscopy work?

Every bond has a unique vibration frequency; bonds absorb radiation with matching frequencies, causing certain frequencies to be missing from the emerging radiation.

What happens inside an infrared spectrometer?

A beam of infrared radiation is passed through the sample, and frequencies absorbed result in a graph of intensity against frequency.

What do the troughs on an infrared spectrum show?

They indicate frequencies where radiation has been absorbed; matching to a table helps identify the corresponding bonds.

What is the fingerprint region in infrared spectroscopy?

The area of the infrared spectrum below 1500 cm-1, unique to every compound, used to identify compounds.

How is the fingerprint region used to identify compounds?

The pattern of the fingerprint region is matched to a database on a computer for accurate compound identification.

What kind of intermolecular forces do alcohols have and why?

Hydrogen bonding, due to the electronegativity difference in the OH bond.

How do alcohols’ melting points and boiling points compare to hydrocarbons of similar carbon chain lengths and why?

Alcohols have higher melting points and boiling points because they have hydrogen bonding which is stronger than Van der Waals forces.

Are alcohols soluble in water and how does solubility depend on chain length?

Alcohols are soluble when short chain because OH can hydrogen bond with water, but insoluble when long chain due to non-polarity of the C-H bond.

What are the advantages and disadvantages of ethanol production from crude oil?

Advantages: fast, continuous process with high purity. Disadvantages: not renewable as it comes from crude oil.

How can ethanol be made by fermentation?

Plant carbohydrates are broken down and fermented by enzymes in yeast to produce ethanol.

What conditions are needed for fermentation to produce ethanol?

Enzymes in yeast as catalyst, 35°C, and anaerobic conditions.

What are the advantages and disadvantages of ethanol production from plants?

Advantages: renewable source. Disadvantages: slow batch process; enzymes stop working at 15% alcohol, necessitating fractional distillation.

In the future, how might most ethene be made and why is it not made this way currently?

By dehydrating ethanol made by fermentation; it is currently not economical.

Define carbon neutral.

No net addition of CO2 to the atmosphere; CO2 released during combustion equals CO2 absorbed by the plants.

How could using ethanol in petrol engines be considered carbon neutral?

The carbon dioxide released during fermentation and combustion equals the carbon dioxide absorbed while the plants grow.

Why might using ethanol not be entirely carbon neutral?

Other 'carbon costs' are associated, such as transport.

What is a commercial fuel that uses ethanol and what else does it contain?

Methylated spirits contain methanol (toxic, preventing consumption).

What physical conditions are required for the elimination reaction from alcohols to alkenes?

Excess hot concentrated sulfuric acid or passing vapor over hot aluminum oxide.

What conditions are needed to partially oxidize a primary alcohol?

Dilute sulfuric acid, potassium dichromate (VI), distilling product as it’s produced, gentle heating.

What conditions are needed for the complete oxidation of alcohols?

Concentrated sulfuric acid, potassium dichromate (VI), reflux for about 20 mins, strong heating.

Why can a tertiary alcohol not be oxidized?

A carbon-carbon bond would have to break.

What conditions are required for the oxidation of a secondary alcohol?

Concentrated sulfuric acid, potassium dichromate (VI), reflux for about 20 mins, strong heating.

What is an aldehyde and what is its functional group?

A molecule with a C=O group at the end of a carbon chain; the carbonyl functional group (C=O).

What is a ketone and what is its functional group?

A molecule with a C=O group in the middle of a carbon chain; the carbonyl functional group (C=O).

What is a carboxylic acid and what is its functional group?

A molecule with a COOH group at the end of a carbon chain; the carboxyl functional group made up of a carbonyl C=O and hydroxyl -OH group.

What is in Tollens’ reagent and how does it react with substances?

Silver nitrate in NH3 (aq) oxidizes aldehydes but not ketones; complex silver (I) ions are reduced to Ag(s).

How do you perform the Tollens’ test?

Add equal volumes of the substance being tested and Tollens' reagent to a test tube, heat in a water bath for 10 mins and observe any changes.

What is the result of the Tollens’ test for aldehydes and ketones?

Aldehydes produce a silver mirror (solid Ag); ketones show no visible change.

What is in Fehling’s and how does it react with substances?

Blue copper (II) complex ions that act as a gentle oxidizing agent, reduced to Cu+ ions (brick red).

What results do aldehydes and ketones give in the Fehling’s test?

Aldehydes produce a brick red precipitate; ketones show no visible change.

Why is there no rotation about the C=C double bond?

Due to the π (pi) orbital - electron density above and below the single bond, which holds the carbon atoms in place.

Are alkenes more or less reactive than alkanes? Why?

More reactive, due to high electron density of the double bond and the fact that the pi-bond is slightly easier to break.

What are the three kinds of isomers that alkenes can have?

1. Chain isomers (branched chains), 2. Position isomers (C=C on different carbon atom), 3. Geometric E-Z isomers (Z is when 2 highest atomic number chains are on the same side of the double bond; E is when they're on opposite sides).

What is an electrophile?

Electron deficient atoms/ions which accept a pair of electrons from the C=C double bond.

What is the most stable kind of carbocation intermediate? Why?

A tertiary carbocation because alkyl groups have a positive inductive effect, making it more stable when bonded to other carbon atoms.

What conditions are needed for the electrophilic addition of a halogen molecule to an alkene?

Room temperature and an organic solvent.

How does a molecule with a non-polar bond react as if it is an electrophile?

The C=C double bond with high electron density induces a temporary dipole in the halogen molecule, leading to attraction of the δ+ atom to the double bond.

How would you turn the product from sulfuric acid + ethene into an alcohol? What does this show about sulfuric acid?

Add water; H₂SO₄ reforms, showing it catalyses the hydration of alkenes.

What is an addition polymer?

Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule.

What are monomers and what form do they usually take?

Molecules that combine to form a polymer; usually have a C=C bond which breaks to form a repeating pattern.

What are plasticisers?

Small molecules that get between polymer chains to force them apart and allow them to slide over one another.

How do the physical properties of PVC change due to a plasticiser?

PVC with a plasticiser becomes flexible and is used for aprons; without a plasticiser, PVC is rigid and used for drainpipes.

Why do compounds mainly containing C-C and C-H bonds not decompose easily?

The bonds are non-polar and are not attacked by enzymes.

Why is a lack of biodegradability in compounds with C-C or C-H bonds a problem?

Disposal is very problematic.

What is feedstock recycling?

Plastics heated to a temperature which breaks polymer bonds, leaving original monomers that can be made into new plastics.

What is a problem with recycling thermosoftening plastics?

Each time they are melted and remoulded, their properties degrade, so they can only be remoulded a limited number of times.

What is a skeletal formula?

A skeletal formula is drawn as lines with each vertex representing a carbon atom, where carbon atoms are not drawn, and it is assumed each C atom has all unspecified bonds as C-H.

What suffix is used for compounds with no double bonds?

-ane

What is the suffix for compounds with at least one double bond?

-ene

What suffix is used for alcohols?

-ol

What is the suffix for aldehydes?

-al

What suffix is used for ketones?

-one

What suffix denotes a carboxylic acid?

-oic acid

What is the prefix for a CH3 group?

methyl-

What prefix is used for a C2H5 group?

ethyl-

What is the prefix for a C3H7 group?

propyl-

What prefix is used for a C4H9 group?

butyl-

What is the prefix for a Cl group?

chloro-

What prefix denotes a Br group?

bromo-

What is the prefix for an I group?

iodo-

What is functional group isomerism?

Functional group isomerism occurs when same atoms are arranged differently to form different functional groups.

Define stereoisomerism.

Stereoisomerism occurs when molecules have the same structural and molecular formula, but a different arrangement of atoms in space.

What is E-Z isomerism?

E-Z isomerism is caused by limited rotation about C=C double bonds, determined by the position of the two substituents with the highest atomic number.

How is the E isomer defined in E-Z isomerism?

The E isomer has the two highest atomic number substituents on opposite sides of the double bond.

What characterizes the Z isomer in E-Z isomerism?

The Z isomer has the two highest atomic number substituents on the same side of the double bond.

Why are alkanes insoluble in water?

Because hydrogen bonds in water are stronger than alkanes’ van der Waals forces of attraction.

What is crude oil and how is it formed?

Crude oil is a mixture of fractions (hydrocarbons with similar boiling points and properties) formed at high temperatures and pressures deep below the Earth’s surface over millions of years, making it non-renewable.

Name the fractions of crude oil from high to low boiling point.

Gases, gasoline/petrol/naphtha, kerosene/paraffin, diesel oil, lubricating oil/waxes, fuel oil, tar/bitumen.

What is fractional distillation?

It is a process where crude oil is heated until mostly vaporized and then passed into a fractionating tower cooler at the top than the bottom, where liquid fractions are piped off.

What is fracking?

Fracking is a process to extract natural gas from shale rock by drilling into it and forcing pressurized water and sand to fracture the rock.

What are the advantages and disadvantages of fracking?

Advantages include a long-term gas supply and reduced imports. Disadvantages include traffic issues, water usage concerns, pollution risks, small earthquakes, and contribution to global warming.

Why are alkanes cracked?

To convert long-chain alkanes, which are economically less valuable, into shorter-chain alkanes (more valuable as fuels) and alkenes (more reactive for various products).

What are the conditions for catalytic cracking?

Lower temperature (720K), lower pressure (above atmospheric), and a zeolite catalyst (SiO2 and Al2O3) with a honeycomb structure.

What are the five main fuels comprising alkanes?

Methane, butane, propane, petrol (about C8), and paraffin (C10 - C18).

What is incomplete combustion in alkanes?

Combustion in a limited supply of oxygen producing CO (carbon monoxide) which is poisonous and C (carbon - particulates) which can cause global dimming.

What is the environmental impact of carbon dioxide?

Carbon dioxide is a greenhouse gas that contributes to global warming by increasing global temperatures.

What is the environmental impact of water vapor?

Water vapor is a greenhouse gas that also contributes to global warming by increasing global temperatures.

Write equations for desulfurising flue gases.

1) CaO (s) + 2H2O (l) + SO2 (g) + ½O2 (g) → CaSO4.2H2O (s); 2) CaCO3 (s) + SO2 (g) + ½O2 (g) → CaSO4 + CO2 (g).