Organic (Year 2)

These are reduction reactions that reverse the oxidation of alcohols to aldehydes and ketones.

The overall reaction is: Aldehyde/ Ketone + 2[H] -> Alcohol

The NaBH₄ provides the H⁻ nucleophile, while the solution of water provides the H⁺. Therefore, the conditions are aqueous.

This is the mechanism that forms optical isomers (and often a racemic mixture).

The overall reaction is: Aldehyde/ ketone + CN⁻ + H⁺ -> Hydroxynitrile

The conditions are Potassium cyanide followed by dilute sulfuric acid. It is important you say the ‘followed by’ as the acid needs to provide the H⁺ for the O⁻.

They are non-superimposable mirror images of each other.

A mixture that contains an equal proportion of both enantiomers/ optical isomers.

No, it is optically inactive. This means it can’t be used to tell whether enantiomers have been formed.

A chiral carbon, so a carbon atom with 4 different groups attached to it.Note: If a question asks you to circle them, circle the chiral carbons.

HCN is a weak acid, meaning the concentration of CN⁻ ions it forms is too low.

Water is added in the presence of an acid catalyst to produce a carboxylic acid and alcohol.

NaOH is added to form a carboxylate salt and alcohol.

In acid, the reaction is reversible.

In alkaline, the reaction is irreversible.

It allows both the oil and KOH to dissolve as it is a mutual solvent to both.Note: you could also add it makes the reactants ‘miscible’.Note: there was no explanation for WHY it actually is a mutual solvent, so I guess you just need to know that it's a mutual solvent to both (lipids = soluble in ethanol, insoluble in water; KOH = soluble in both ethanol and water).

Methanol is added to vegetable oils in the presence of a strong acid catalyst.Note: a strong alkaline catalyst (NaOH) can also be used and this is preferred in industry.Note 2: the mixture is also warmed.Note 3: remember the reaction is also reversible.

It is nucleophilic addition-elimination.Note: you don’t have to draw this mechanism, but you should know that carboxylic acid + alcohol, like acid chloride + alcohol, is nucleophilic addition-elimination.

H₂ + Nickel catalyst.

H₂SO₄ + HNO₃ → NO₂+ + HSO₄⁻ + H₂ONote: the preferred answer on the mark scheme was: HNO₃ + 2H₂SO₄ → NO₂ + + H₃O⁺ + 2HSO₄− However, they explicitly accepted the top equation I gave so I’d use that one as it combines the two equations seen in the ‘Mechanisms’ section for the nitration of benzene.

Nitrobenzene + 6[H] -> Phenylamine + 2H₂O

This is the equation as it isn’t a normal H₂ + Nickel catalyst reaction. Instead, the nitrobenzene is heated with Sn and concentrated HCl, creating a phenyl ammonium ion, which is then neutralised with NaOH.

Note: H₂ + Nickel catalyst can be used for this conversion, too, but on exams they usually talk about the Sn/HCl method.

It reacts with the water to form an alkyl ammonium ion + OH⁻, forming a basic solution.Note: the reaction is reversible and it is important to note that an alkyl ammonium hydroxide salt doesn’t form.

Due to the reaction described in the note above (amine + water -> alkyl ammonium ion + OH⁻).

A phenylammonium ion forms, which dissolves in water.

First, you have to make a halogenoalkane, as this is needed for both the cyanide and ammonia method.

To do this you need to react the alkane with Cl₂ in the presence of UV light.

Hair conditioners and fabric softeners.Note: this is because they act as cationic surfactants.

The manufacture of cationic surfactants (fabric softeners, hair conditioners).Note: of course only the quaternary alkyl ammonium salts are cationic surfactants, but the use of any amine can be to manufacture these quaternary alkyl ammonium salts.

The C-C bonds in their chain are non-polar and cannot be attacked by nucleophiles, meaning they cannot be hydrolysed.Note: PVC, for example, contains polar C-Cl bonds, but since these aren’t in the chain it is still non-biodegradable.

By heating them with concentrated hydrochloric acid or a concentrated base (usually a hydroxide so alkali).Note: this is in contrast to additional polymers which can only be broken down through burning them.

It would prevent them building up in land fill as they would be able to be broken down by natural processes.

Polyesters don’t, but polyamides do.

Polyamides form hydrogen bonds between the hydrogen on their NH groups and the lone pair on the oxygen on their C=O groups.Note: This is why it’s important to know the examples of polyesters and polyamides I mentioned above - I’ve seen a question where they asked ‘which of these 4 polymers (Terylene, Kevlar, PVC, and poly(something) ) contains hydrogen bonding between its chains?’ and you had to know Kevlar was a polyamide so therefore had hydrogen bonding.

Terylene.Note: this can come in useful in multiple choice questions.

It is poly(chloroethene).

It is an addition polymer made out of chloroethene monomers.

It is hard and brittle so is used to make drain pipes.

It makes it more flexible as it gets between the polymer chains and pushes them apart, weakening the IMFs between the chains, allowing them to slide over each other more easily.

1. Hydrochloric acid + heat

2. Protease in warm conditions (not heat).

An amino acid must have an overall net neutral charge to be a zwitterion, so if it has a COO⁻ or NH₃⁺ in its R group that causes it to have a negative or positive charge, it is not a zwitterion.

Only one enantiomer will be able to form the correct hydrogen/ ionic bonds (interactions) with the active site that allow it to bond and be catalysed, as the functional groups need to be oriented correctly according to the lock-key model.

2-deoxyribose.Note: always include the '2' as it is found on the data sheet.

A nitrogen atom on guanine forms co-ordinate bonds with Pt. When two N atoms from separate strands form this dative covalent bond, this distorts the shape of the DNA molecule and prevents it from replicating.Note: this occurs after the Cl ligands have already been substituted for H₂O ligands, so the H₂O ligands are replaced by the N’s on guanine.

A - alpha helix.

B - beta pleated sheet.

They are immiscible, so the denser liquid will sink to the bottom and can be drained off first.

Add sodium carbonate to neutralise the acid, then separate in a separating funnel.

To avoid the pressure build-up caused by the releasing of gas (CO₂), preventing the stopper blowing out.

The method is filtration.

There is gravity filtration where the solution is poured through V-shaped filter paper into a funnel into a beaker.

There is vacuum filtration where the solution is poured through a Buchner funnel into a side arm flask that has a side arm to a vacuum source.Note: notice the Buchner funnel has its filter paper laid horizontally.

It is vacuum filtration where the pressure is reduced in the container the product is being filtered into, drawing the liquid through the filter paper.

The equipment needed is a Buchner funnel containing filter paper with a side arm flask connected to a vacuum pump.

Note that a Buchner funnel has a flat bottom. Don’t draw a funnel with a triangular bottom as this is a Hirsch funnel.

Theoretical:

1. Side reactions occur, so by-products are made instead of the expected products.

2. The reagents used may be impure.

3. The reaction is incomplete.

Practical:

1. Some of the product is lost in the purification steps, such as in transfer between apparatus.

2. Some product is lost in distillation.

The product wasn’t fully dried, so the mass of water is being measured too.

To ensure the hot solution is saturated so crystals form upon cooling.

Because the solubility decreases as temperature decreases, meaning more crystals form as it cools, allowing a higher yield of the solid to be obtained.

To allow air to pass through the sample, not just around it.

This creates better drying, but doesn’t squeeze water out of the crystals.

The purpose is to wash away any soluble impurities/ any ethanolic solution on the product.

It is important that only a small amount of cold ethanol is added to avoid aspirin getting dissolved in the ethanol.

Water.

It can be minimised by pressing the sample between dry filter papers.

The temperature on the thermometer could be different to the actual temperature of the sample, as the thermometer measures the temperature next to the capillary tube, not inside of it.

It’s corrosive.Note: you could’ve also said skin burn or permanent eye damage, but not just ‘irritant’.

They are good solvents for ¹H NMR because they are inert and they don’t contain any ¹H atoms, meaning they don’t produce a signal. CCl₄ is non-polar so is a suitable solvent for non-polar molecules. CDCl3 is polar so is a suitable solvent for polar molecules.

The adjacent C has no non-equivalent H attached.Note: this means that no splitting takes place.

They are both singlets.

Note: at first I didn’t realise you only count the hydrogens on carbons adjacent to the whole environment, and don’t count the hydrogens within a given environment.

Answer:

CH₃-O-CH₂CH₂Cl

Explanation:

1. There is an integration ratio of 2:2:3.

2. The peak at 3.95 is caused by ClCH₂ and it is triplet as it is next to a CH₂.

3. The peak at 3.65 is caused by O-CH₂ and it is triplet as it is next to a CH₂(Cl)

4. The peak at 3.35 is caused by O-CH₃ and it is a singlet as there is no adjacent HNote: basically give the integration ratio, then explain what caused each peak and explain the splitting patterns.

The balance between its solubility in the mobile phase and the retention by the stationary phase.Note: the words ‘solubility’ and ‘retention’ are preferred. You can also say ‘relative affinity for the mobile and stationary phase’.Note 2: this is also the explanation for why different compounds separate in chromatography - ‘they have differences in the balance between solubility in the mobile phase and retention by the stationary phase.’

If it is added to a depth above the starting line, the sample will dissolve directly into the solvent, meaning it won’t be able to move up the plate with the solvent.Note: ‘dissolve’ seems to be the key word.

To prevent the solvent vapour escaping, which allows the atmosphere in the beaker to remain saturated with the solvent vapour.

You must wear plastic gloves when handling the TLC plate to prevent contamination from the hands to the plate.

Mass spectrometry is used to analyse them.