Reaction Conditions Year 13 OCR Chemistry A

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What is the nitration of benzene?
An electrophilic substitution reaction where a hydrogen atom is exchanged for a nitro group (NO2)
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What are the reagents for the nitration of benzene?
Benzene, concentrated nitric acid and concentrated sulfuric acid as a catalyst
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How do you perform nitration of benzene?
The conc. nitric acid and conc. sulfuric acid are mixed in a flask in an ice bath. Benzene then added and a reflux condenser set up, keeping the mixture at 50 degrees celcius
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What are the reagents for the halogentation of benzene?
Benzene and a halogen carrier such as iron (which forms an iron halide in situ), iron halides or aluminium halides which generate a positive halogen ion and act as a catalyst
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What is a Fridel-Crafts reaction?
A substitution reaction where hydrogen is exchanged for an alkyl or acyl chain
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What is an acylation reaction?
A Friedel-Crafts reaction where an acyl chloride is used as a halogen carrier to substitute just one hydrogen atom
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What are the reagents and conditions in acylation?
Acyl chloride, benzene, aluminium chloride catalyst under reflux at 60 degrees celsius for 30 minutes
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What are the products of acylation and why?
As the carbonyl group withdraws electrons from the aromatic ring, a less reactive ketone is made. So only one substitution can occur
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How are haloalkanes used in Fridel-Crafts reactions?
Haloalkanes are mixed with a halogen carrier such as iron chloride which acts as a catalyst and is regenerated at the end. A reactive carbocation ion is made which undergoes electrophillic substitution where a H is substituted for an alkyl group
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What are the products of the haloalkane Fridel-Crafts reaction?
Multiple substitutions are likely so a mixture of products is made. The catalyst is regenerated and the hydrogen reacts with the halide ion from the haloalkane
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How are the products of haloalkane Fridel-Crafts reactions separated?
Fractional distillation or chromatography. The yield of singly substituted product can be improved by adding excess benzene.
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Why does phenol partially dissociate in water?
It is a weak acid
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What are the products when phenol reacts with a strong bases?
A salt and water as it acts like a weak acid
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As a weak acid what doesn't phenol react with?
It doesn't react with carbonates but it does with strong bases such as sodium hydroxide
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What are the reagents, products and conditions for the oxidation of aldehydes?
Aldehydes are reacted with potassium dichromate and sulfuric acid under reflux to produce a carboxylic acid. The colour changes from orange to green
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What are the reagents, products and conditions for the reduction of carbonyls?
NaBH4 is a reducing agent which acts a source of hydride ions involved in electrophillic addition (reduction) of carbonyls to alcohols. An intermediate such as ethanol is also used.
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What are the reagents, products and condtions for the reaction of cyanide with carbonyls?
A source of cyanide (eg. hydrogen cyanide, sodium cyanide), acidify the reaction to increase the polarity of the C=O bond otherwise the reaction won't occur. A hydroxynitrile is formed and it allows further carbon atoms to be added to a molecule
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What is 2,4 DNP (Brady's Reagent) used for?
It is an orange transparent mixture but when added to an aldehyde or ketone a yellow/orange precipitate of 2,4dinitrophenylhydrazone derivative is seen
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What is Tollens' Reagent used for?
It is used to distiguish between an aldehyde and a ketone. A silver mirror is produced with an aldehyde
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How is Tollens reagent made?
1. Sodium hydroxide solution is added to silver nirate solution until a brown precipitate is formed. 2. Dilute ammonia is added drop-wise until the brown precipate redissolves
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What happens when Tollens' Reagent is added to to an aldehyde?
The silver ions (1+) are reduced and precipitated out. The aldehyde is oxidised to a carboxylic acid. This is a redox reaction.
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What are the products when a carboxylic reacts with a metal?
Metal salt and hydrogen gas
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What are the products when a carboxylic reacts with a metal oxide?
Metal salt and water
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What are the products when a carboxylic reacts with metal hydroxides?
Metal salt and water
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What are the products when a carboxylic reacts with metal carbonates?
Metal salt, water and carbon dioxide
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What are the products when a carboxylic reacts with a metal hydrogen carbonate (MHCO3)?
Salt, water and carbon dioxide
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What are the reagents and conditions to prepare a small ester?
An alocohol and carboxylic acid are heated gently with a sulfuric acid catalyst. Reversible reaction with a slow rate. Phenol can't be used as the rate is too slow.
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How and why can the ester be separated?
The ester is volatile with the lowest boiling point of the chemicals so it can be separated using distillation. Has to happen quickly to prevent the reverse reaction occuring
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How are large esters prepared?
The reaction mixture is heated under reflux until equilibrium has been established. Ester can be separated using fractional distillation
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How is an acid anhydride made?
By the removal of a water molecule for two carboxylic acid molecules
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How are acid anhydrides used in the preparation of esters?
They react with alcohols, including phenol, to make an ester. Not revserible so has a higher yield. Slow rate but increased by gently warming
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What is a hydrolysis reaction?
A chemical reaction where water breaks down another product
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What are the reagents, products and acidic conditions when an ester undergoes acidic hydrolysis?
Esters are refluxed with a catalyst of hot aqueous acids (eg. dilute HCl) to reversibly make an alocohol and carboxylic acid.
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What are the reagents, products and acidic conditions when an ester undergoes alkaline hydrolysis?
Esters are refluxed with a hot aqueous alkali (eg.KOH) to make an alcohol and a carboxylate salt (where the OH is replaced by O- and postive metal). Not reversible. Used to make soap-saponification
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How do you prepare an acyl chloride?
A carboxylic acid is reacted with liquid SOCl2 at room temperature. The -OH of the acid is substituted for a -Cl atom and sulfur dioxide and hydrogen chloride gas is produced
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How are acyl chlorides used to make esters?
They are reacted with an alcohol. Not reverisble so has a higher yield than with a carboxylic acid. Works with phenols. Violent reaction that produces corrosive fumes of HCl
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How are acyl chlorides used to make carboxylic acids?
A small acyl chloride is added to water and it quickly hydrolyses to produce a carboxylic. This is a very exothermic reaction and fumes of HCl are given off
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How are acyl chlorides used to make primary amides?
An acyl chrloride reacts with a concentrated ammonia solution. A mixture of solid ammonium chloride and a orimary amide obsevred as a white smoke are produced.
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How are acyl chlorides used to make secondary amides?
An acyl chloride is reacted with a cold concenrated solution of a primary amide to produce a secondary amide and HCl.
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What are the reagents and products when a primary amine reacts with a dilute inorganic acid?
An alkylammonium salt is produced
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How are primary aliphatic amines prepared?
Using a sealed tube, a haloalkane, ammonia and ethanol are heated together. Stage 1: the ammonia reacts with the haloalkane to make an ammmonium salt. Stage 2: an additional ammonia molecule reacts to form the amine and ammonium salt. Reversible.
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How are secondary and tertiary amines formed?
React the primary amine with a haloalkane. HCl also produced
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How is a quaternary ammonium saalt produced?
React a tertiary amine with a haloalkane (eg.chloropropane). N+ and Cl- and each hydrogen has been replaced by an alkyl chain
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What are the products and reagents to produce aromatic amines from nitroarenes?
Nitrobenzene is reduced (shown by [H]) then NaOH is added to neutralise the reaction and remove the excess HCl to produce the amine
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What are the reaction conditions to produce aromatic amines from nitroarenes?
Reflux at 100 degrees celcius. Reducing agent made in situ by using a mixture of tin and conc. hydrochloric acid. After 30minutes a strong alkali (eg.NaOH) is added.
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How us an aromatic aime separated from the reaction mixture?
It is a multi-stage process that includes steam distilllation, solvent extraction and further distillation.
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What is the product when a zwitterion has the pH of it's enviroment lowered (more hydrogen ions)?
Amino acid is acting as a base and accepts a proton from the acid forming an NH3+ group
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What is the product when a zwitterion has the pH of it's enviroment increased (more -OH ions)?
Amino acid is acting as an acid and donates a proton to the hydroxide ion from the OH od the COOH group to form an O- on the zwitterion and water
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How are addition polymers made?
Monomers have at least one C=C which breaks and joins the other monomers together. Only one product eg. polyethene from from many ethene monomers
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How are condensation polymers made?
Two different monomers with two different functional groups react to form a polymer and another small molecule often water. Examples: nylon and polyester
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How are polyesters made?
Condensation polymer made from a dicarboxylic acid and a diol. An ester link is formed between the two. Water is produced. Can also be made from one monomer with both a -COOH and -OH group
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How are polyamides made?
Condensation polymer made from a dicarboxylic acid and a diamine. An amide link is formed betweeen the two. Water is produced. Can also be made from one monomer with a -COOH and -NH2 group
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What happens to a polyester under acid hydrolysis?
Polyester is reacted with a strong aqueous acid to produce a diol and dicarboxylic acid. Slow rate of reaction.
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What happens to a polyester under alkali hydrolysis?
Polyester is reacted with hot sodium hydroxide to prodice a diol and salt of the dicaroboxylic acid where the -OH of the carboxylic acid becomes O-Na+
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What happens to a polyamide under acid hydrolysis?
A polyamide is reacted with strong aqueous acid to rpdocue a diammonium salt and a dicarboxylic acid. Very fast rate
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What happens to a polyamide under alkaline hydrolysis?
A polyamide is reacted with hot sodium hydroxide solution to produce a diamine nad the salt of the dicaroboxylic acid where the -OH od -COOH becomes O-Na+
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What happens in nucleophillic substitution of haloalkanes with cyanide?
A haloalkane is mixed with KCN and heeated under reflux with ethanol as the solvent to ensure cyanide is the nucleophile. Cyanide takes the place of the halogen and increases the carbon chain length. Potassium halide is also produced.
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What happens in nucelophillic addition with carbonyls and a cyanide nucelophile?
The carbon in the C=O has a slight + charge so is susceptible to nucleophillic attack by -CN, extending the C chain length. The pi bond of C=O opens and the O accepts a pair of e- and H from HCN , becomes an -OH and forms a hydroxynitrile
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What are the reagents, products and conditions used to form amines from nitriles?
Nitriles are reduced by reacting directly with two molecules of hydrogen gas to make a primary aliphatic amine. A nickel catalyst is to lower the activation energy and it is heated to 150 degrees Celsius at raised presuure
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What other compound can also be used to reduce a nitrile to an amine?
Lithiumtetrahydridoaluminate(III) LiAlH4, a reducing agent, represent as 4[H] in an equation to make a primary aliphatic amine.
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What are the products and conditions for the hydrolysis of nitriles?
They initially form an amide then an ammonium salt. The 2nd reaction is not significant as it is so slow. Rate can be increased by using a strong acid catalyst and heating under reflux
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What are the reagents and products when nitriles undergo acid hydrolysis?
Nitriles are reacted with water and HCL (or any strong acid) to form a carboxylic acid and an inorganic ammonium salt
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What is alkylation?
A reaction where hydrocarbon chains are added to an organic compound. Electrophillic substitution
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What are the reagents and product of alkylation?
An aromatic compound, a haloalkne and a strong Lewis acid catalyst (eg. FeCl3 is a Friedel-Crafts catalyst as it is an electron pair acceptor) are reacted together to produce an alkylbenzene, hydrogen halide (eg.HCl if FeCl3 used) and the catalyst
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Card 2

Front

What are the reagents for the nitration of benzene?

Back

Benzene, concentrated nitric acid and concentrated sulfuric acid as a catalyst

Card 3

Front

How do you perform nitration of benzene?

Back

Preview of the front of card 3

Card 4

Front

What are the reagents for the halogentation of benzene?

Back

Preview of the front of card 4

Card 5

Front

What is a Fridel-Crafts reaction?

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Preview of the front of card 5
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