Chemistry - Organic

What is a disproportionation reaction

Where both oxidation and reduction take place .

Problems with Chlorine reacting with water in sunlight

The chlorine is regularly lost from water so has to be regularly topped up.

What are the properties of Catalytic Cracking?

High temperature and normal pressure but with a zeolite catalyst to produce aromatic compounds with carbon rings

Equation for Catalytic converters?

2CO + 2NO → 2CO2 + N2

Equation for flue gas desulphurization?

CaO + SO2 → CaSO3

What are the problems with CFC’s?

The C-Cl bonds in CFCs are broken by ultraviolet radiation, releasing chlorine radicals. These act as catalysts in ozone depletion.

What are the safer alternatives to CFCs?

HFCs

Why are halogenoalkanes more reactive than normal alkanes?

The carbon halogen bond becomes a dipole. Reactivity of the halogenoalkanes increases as the bond gets weaker down the group.

Why are the formation of major products favoured than minor products?

Major products are made from a more stable carbocation. This stability arises from a greater positive inductive effect.

How to identify alkenes?

Use bromine water, if a double bond is present the solution will go from orange-brown to colourless.

How are branched chain polymers formed?

High pressures and temperatures produce branched chain polymers with weak intermolecular forces

How are straight chain polymers formed?

Low temperatures and pressures produce these with strong intermolecular forces.

What is biofuel?

Fuel made from recently living biological material

What are the 3 step processes and their equations in creating biofuel?

What are some properties of polymers that make it good for the production of plastics?

They have multiple strong, non polar covalent bonds.

What is observed when an alcohol is oxidised?

Colour change from orange to green

Why is flue gas desulphurisation needed?

To remove sulphur impurities that react to form a weak H2SO4.

Properties of thermal cracking

High Temperature and pressure to produce more alkenes than alkanes

What is formed when primary alcohols are heated with acidified potassium dichromate?

Aldehydes

How can primary alcohols oxidise to form caboxylic acids?

When their aldehyde is heated further under reflux

Why are some polymers unreactive?

They have multiple non-polar covalent bonds

What is formed when secondary alcohols are heated with acidified potassium dichromate?

A ketone

What does reacting an acyl chloride/acid anhydride with water make?

Carboxylic acid + HCl/Carboxylic acid

What does reacting an acyl chloride/acid anhydride with alcohol make?

Ester + HCl/Carboxylic acid

What does reacting an acyl chloride/acid anhydride with Ammonia make?

Amide + HCl/Carboxylic Acid

What does reacting an acyl chloride/acid anhydride with a primary amine make?

N-substituted amide + HCl/Carboxylic acid

What is stereoisomerism?

Two molecules with the same molecular and structural formula but the atoms are arranged differently in 3D space

Equation for the decomposition of ozone.

cl. + o3 → clo. + o2

clo. + o3 → 2o2 + cl.

Why are catalytic converters used?

They remove CO, NO and unburned hydrocarbons. They are lined with a platinum catalyst to increase surface area.

How can you distinguish acyl chlorides?

Add silver nitrate solution and white ppt of silver chloride should form

How does the shape of an organic molecule affect bp and mp?

Straight chain alkanes have a higher bp and mp because a greater surface area is in contanct with many more molecules so many more vdw forces can be made.

Why is heating under reflux used?

The reaction can run at the solvents boiling point for longer to ensure the reaction goes to completion, ensuring a higher yield without losing vapour materials.

Why is KCN used instead of HCN in cyanide mechanisms?

HCN is toxic and hard to store as a gas. KCN will completely ionise and HCN only partially ionises.

How are racemic mixtures produced?

The planar carbonyl group (C=O) means that the nucleophile can attack from either side with equal probability. The aldehyde/ketone must also be unsymmetrical.

Why are acid anyhdrides preferred to acyl chlorides?

Cheaper, less corrosive, no corrosive hcl produced, less exothermic

How are triglyceride esters formed?

From the esterification of glycerol

What is another name for glycerol?

propane-1,2,3-triol

Draw the structure of an acid anhydride (use R for any other groups)

What is the name of the mechanism that acyl chlorides/acid anhydrides undergo?

Nucleophilic Addition - Elimination

What happens in acidic hydrolysis from an ester?

Acidic conditions and a H+ ion catalyst so it is a slow process. It happens in equilibrium so yeild of the alcohol and carboxylic acid are always low.

What catalyst is used to form esters from alcohols and carboxylic acids?

concentrated sulfuric acid

Test for aldehydes with fehlings solution

Changes colour from blue to a red ppt.

What happens in basic hydrolysis to an ester?

Ester will react with a base (NaOH) forming an alcohol and a carboxylate salt. The reaction goes to completion so has a higher percentage yield. You can regenerate the carboxylic acid by reacting the salt with a strong acid.

How are soaps formed?

When a triglyceride ester reacts with a base like NaOH, forming glycerol and 3 moles of a sodium soap.

How are triglyceride esters formed?

When glycerol reacts with 3 moles of a carboxylic acid.

How is biodeisel formed?

When a triglyceride ester reacts with methanol, forming glycerol and 3 moles of a methyl ester.

How does infrared spectroscopy work?

The bond that joins a pair of atoms is always vibrating. The stronger bonds vibrate faster at a higher frequency. This bond, will absorb a frequency of IR radiation equal to the natural frequency of the bond. The radiation emerged can be passed through an instrument where it plots a graph of intensity against frequency. The dips represent frequencies of specific bonds in the sample being absorbed.

Why are CCl4 and CDCl3 used in C13 and HNmr spec?

The samples being tested are dissolved in these inert compounds that have no hydrogen atoms. This means that they will not affect the proton nmr. They do contain carbon atoms so will show a peak on the Carbon nmr but it is known where these peaks are. CCl4 itself is non-polar so its good for dissolving non-polar organic compounds, vice versa for CDCl3.

How do you test for an alcohol?

Add acidified potassium dichromate, primary and secondary alcohols will change from orange dichromate ions to green chromium ions. Tertiary alcohols experience no change

Test for an aldehyde?

Tollen’s Reagent will form a silver mirror.

Test for a halogenoalkane?

Sodium hydroxide solution warmed then add silver nitrate and dilute nitric acid. Add the haloalkane and a silver halide ppt should form.

How can a PVC be made flexible?

Adding a plasticiser

What is the structure of the benzene molecule?

A planar hexagonal molecule with 6 carbon atoms. It has a 120 degree bond angle with all C-C bonds equal in length.

What is the bonding in the benzene molecule?

Each Carbon makes three covalent bonds, 2 to carbon and 1 to hydrogen. Delocalised electrons in the p orbital overlap to form an electron ring above and below the plane of the molecule.

What was the original structure of benzene?

A hexagonal ring with alternating double and single bonds.

Why is the new model of benzene more thermodynamically stable than the old structure of benzene?

It has a delocalised electron orbital

What is the difference in stability between benzene and the hypothetical cyclohexa-1,3,5-triene?

Benzene is less exothermic and more stable by 152 kJ mol^-1

What is the order of the bonds of increasing bond length in cyclohexatriene and benzene?

c=c, c-c bond in benzene, normal c-c bond

What is the name for aromatic compounds that contain a benzene ring?

Arenes

What reactions does benzene undergo?

Electrophilic substitution

In nitration of benzene, give the reagents needed to produce the electrophile NO2+

Concentrated H2SO4 and HNO3

Give the equation for the generation of the electrophile NO2+.

H2SO4 + HNO3 → HSO4- + H2O + NO2+

Which reagent in making the NO2+ electrophile is the base?

HNO3 as it accepts the H+ proton

What is formed in the acylation of benzene?

A phenyl ketone

What is the electrophile in the acylation of benzene and how is it formed?

RCO+, formed by reacting an acyl chloride/anhydride with aluminium chloride which is the catalyst.

What is the equation to form the RCO+ electrophile?

AlCl3 + RCOCl → AlCl4- + RCO+

Why is aluminium chloride a good choice for forming the RCO+ electrophile?

It polarises the electron cloud around the chloride ion, causing it to be removed so the catalyst gains it.

How is the catalyst regenerated from AlCl4-?

AlCl4- + H+ → AlCl3 + HCl

Why does NMR sepctroscopy work?

Different bond environments absorb different amounts of energy, therefore they show as different peaks on a spectrum.

Why is TMS used in NMR spectroscopy?

It is added along with the organic molecule to be used as a standard. It will show as one peak at 0ppm on the x axis. It is inert and non-toxic and can be removed from the sample easily as it has a low boiling point.

In what solvent should samples that are being analysed in Proton NMR be dissolved in, and why are these solvents used?

CCl4 or CDCl4 as they are non polar and they do not contain any hydrogen atoms so will not produce any peaks on the spectrum.

How can you classify amines in terms of them being 1^o, 2^o or 3^o ?

The number of R groups bonded to the nitrogen is equal to the class.

For amines, what do you name the benzene group attached to the nitrogen?

phenyl

If other functional groups of higher priority are present, what is used instead of amine?

amino at the beginning of the name

How can ammonia and amines behave as nucleophiles?

They have an electron pair to donate

How can ammonia and amines behave as a base?

They have a lone pair to accept a H+ ion.

What type of amines are the better bases and why?

Secondary Amines as they have a greater electron density so lone pairs are more available to accept a H+ ion

How are some amines better bases?

More alkyl groups attached to the nitrogen push the electron density towards the nitrogen, making it more available.

Why is phenylamine not a good base?

Electron ring in benzene is electron withdrawing so the nitrogen lone pair becomes partially delocalised onto the ring, making them less available for protonation

How can primary amines be formed in a 1 step process?

Nucleophilic substitution with excess ammonia

What is the 2 step process to form primary amines?

Nucleophilic substitution reaction (ethanol) with KCN and then reduction with 2H2 under a nickel catalyst.

Why are the advantages and disadvantages of using the 1 step process to form primary amines?

Yield is higher, no toxic or flammable substances. Primary amine produced is impure and can react further with more of the haloalkane

In the further substitution reactions, how do you form the amine as the major product?

React the haloalkane with excess ammonia

In the further substitution reactions, how do you form the QAS as the major product?

React ammonia with excess haloalkane

How is phenylamine formed?

Reduction of nitrobenzene by HCl with a tin catalyst followed by NaOH

What is the equation for the formation of phenylamine from nitrobenzene?

C6H5NO2 + 6[H] → C6H5NH2 + 2H2O

What are phenylamines commonly used for?

Dyes

What can happen to the phenylamine after its production?

It can react with excess HCl and become protonated to form phenylammonium chloride

Draw the structure of phenylammonium chloride.

How is the phenylamine reformed after the formaiton of phenylammonium chloride?

Reaction with NaOH

What is the equation for the reaciton of phenylammonium chloride with NaOH?

Why is phenylamine insoluble in water compared to phenylammoniumchloride which is soluble?

Phenylamine contains hydrogen bonds and a non-polar phenyl group which prevents it from dissolving. Phenylammonium chloride is an ionic salt so its ions can dissociate in water.

What are the two functional groups in a amino acid molecule?

Primary amine and carboxylic acid

What about the amino acid makes it able to form enantiomers?

The chiral carbon

Since the amino acid can react as a base and acid, what does this mean?

It is amphoteric

Draw the basic structure of an amino acid.

What is the zwitterion of an amino acid?

When the carboxylic acid group loses a proton which the amine group gains

In acidic conditions, what happens to the zwitterion?

The carboxylic acid group gains a proton

In basic conditions, what happens to the zwitterion?

A proton is removed from the amine group and added to a hydroxide ion to make water.

What method can be used to separate a mixture of amino acids?

Thin Layer Chromatography