Chemistry - Rings, Polymers and Analysis - F324 - Rings, Acids and Amines (1) Flashcards
What are arenes?
Arenes are aromatic carbons containing one or more benzene rings.
What are examples of natural sources of benzene?
Natural sources of benzene include volcanoes and forest fires.
Who suggested that there were two forms of benzene which were in rapid equilibrium?
Kekulé suggested that there were two forms of benzene which were in rapid equilibrium.
Who discovered that all the bonds in benzene were of the same length and bond angle?
Kathleen Lonsdale discovered that all the bonds in benzene were of the same length and their bond angle.
What is the bond angle of the bonds in benzene?
120o
What method did Kathleen Lonsdale use to make her discoveries?
X-ray diffraction
What length are all the bonds in benzene?
All of the bonds in benzene are 0.139nm
What length is a C-C single bond?
A C-C single bond is 0.153nm.
What length is a C=C double bond?
A C=C double bond is 0.134nm.
What is the enthalpy change of hydrogenation of a C=C double bond?
The enthalpy change of hydrogenation of a C=C double bond is -120kJmol-1.
What is the enthalpy change of hydrogenation of the bonds in benzene?
The enthalpy change of hydrogenation of a bond in benzene is -208kJmol-1
What about benzene’s structure make it more stable and less reactive?
The delocalised pi electrons above and below the plane of the benzene ring mean it is more stable.
What are the most common type (addition, substitution, elimination) of reactions in benzene chemistry?
Substitution reactions are the most common type of reaction in benzene chemistry.
What conditions does the nitration of benzene require?
Benzene will react with concentrated nitric acid and sulphuric acid (the catalyst) at 50oC
What is the catalyst in the reaction of benzene with nitric acid to nitrate the benzene ring?
Concentrated sulphuric acid is the catalyst in the nitration of benzene.
What happens in the nitration of benzene reaction if the temperature exceeds 50oC?
If the temperature exceeds 50oC then more than one nitro group is substituted onto the benzene ring.
What are the uses of nitrobenzene?
Nitrobenzene is an important starting material in the preparation of dyes, pesticides and pharmaceuticals.
Benzene will react with halogens in the presence of what?
Benzene will react with halogens in the presence of a halogen carrier, which is the catalyst.
Why do electrophilic substitution reactions take place in benzene?
Electrophilic substitution reactions take place because of the delocalised ring of electrons above and below the plane of carbon atoms.
In the nitration of benzene, what is the electrophile that the sulphuric acid helps generate?
The nitryl cation, or nitronium ion, which has the formula NO2+.
What are the phenols?
The phenols are a class of organic compound where the hydroxyl group is attached directly onto the benzene ring.
What state is phenol in at RTP?
Phenol is a solid at RTP.
What makes phenol slightly soluble in water?
The OH group can form hydrogen bonds with water making it slightly soluble.
What is formed when phenol is dissolved in water?
When phenol is dissolved in water, phenols form a weak acidic solution by losing an H+ from the OH group.
What is produced when a reactive metal is added to phenol?
The metal effervesces and hydrogen gas is given off.
What happens when bromine water is added to phenol?
The orange colour of bromine water disappears and a white precipitate is formed.
Why does bromine react more readily with phenol than with benzene?
Bromine reacts more readily with phenol because the lone pair on the oxygen is delocalised into the benzene ring creating a greater electron density able of polarising a bromine molecule.
What use did phenol have for many years?
Phenol (carbolic acid) was used as an antiseptic for many years.
What is the functional group found in aldehydes and ketones?
The C=O functional group is found in aldehydes and ketones.
What is a suitable oxidising agent for primary and secondary alcohols?
Acidified dichromate ions (H+/Cr2O72-) are a suitable oxidising agent.
Define reflux.
Reflux is the continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry.
Carbonyl compounds can be reduced to alcohols using what reducing agent?
Carbonyl compounds can be reduced to alcohols using a reducing agent such as sodium tetrahydridoborate (III) NaBH4.
Aldehydes and ketones react with NaBH4 in what type of reaction?
Aldehydes and ketones react with NaBH4 in nucleophilic addition reactions.
Aldehydes and ketones can be detected using which reagent?
Aldehydes and ketones can be detected using the reagent 2,4-dinitrophenylhydrazine (2,4-DNP).
What is 2,4-DNP made up of?
2,4-DNP is a mixture of methanol and sulphuric acid.
What is 2,4-DNP also known as?
2,4-DNP is also known as Brady’s reagent.
What happens when Brady’s reagent is added to an aldehyde or ketone?
When Brady’s reagent is added to an aldehyde or ketone then a yellow or orange precipitate is formed.
Which reagent can be used to distinguish between aldehydes and ketones?
Tollen’s reagent can be used to distinguish between aldehydes and ketones.
Tollen’s is a weak what?
Tollen’s is a weak oxidising agent.
It can oxidise aldehydes to carboxylic acids.
What do you expect to see when Tollen’s is added to an aldehyde and a ketone?
When Tollen’s is added to an aldehyde a silver mirror is formed.
When Tollen’s is added to a ketone, nothing happens.
How do you identify a 2,4-DNP derivative conclusively?
Filtered, recrystalised, allowed to dry, melting point is compared to a database.
What chain length of carboxylic acid is soluble in water?
Short chain (1-4 carbons) carboxylic acids are very soluble in water.
Salts formed from carboxylic acids are known as what?
Carboxylates are salts formed from carboxylic acids.
What is esterification?
Esterification is the reaction of an alcohol with a carboxylic acid to produce an ester and water.
What is often used as the catalyst in the preparation of esters?
Concentrated sulphuric acid is often used as the acid catalyst in the preparation of esters.
How else may esters be produced, other than the reaction of an alcohol with a carboxylic acid?
Esters may also be produced by the reaction of an acid anhydride with an alcohol.
Which method of ester production gives a better yield?
Heating an acid anhydride with an alcohol gives the best yield.
In the reaction of acid anhydrides with alcohol to form an ester, what is the byproduct?
A carboxylic acid is the byproduct of the reaction of an acid anhydride with an alcohol.
What conditions are required for acid hydrolysis of esters?
In acid hydrolysis, the ester is heated under reflux with dilute hydrochloric or sulphuric acid.
What conditions are required for the alkaline hydrolysis of esters?
In alkaline hydrolysis of esters, aqueous sodium or potassium hydroxide is heated under reflux with the ester.
What is/are the product(s) of acid hydrolysis of esters?
The alcohol and the carboxylic acid are the products.
What is/are the product(s) of alkaline hydrolysis of esters?
Forms the sodium salt of the carboxylic acid and an alcohol.
Is alkaline or acid hydrolysis of esters non-reversible?
Alkaline hydrolysis of esters is non-reversible.
What are triglycerides made up of?
Triglycerides are triesters of propan-1,2,3-triol and three fatty acid molecules.
In mono-unsaturated fatty acids, where is the double bond commonly found?
In mono-unsaturated fatty acids, the double bond is usually found between carbons 9 and 10.
What is cis-trans isomerism?
Cis-trans isomerism is a special type of E/Z isomerism in which each carbon of the C=C double bond carries one atom or group that is the same.
Do cis fatty acids usually exist as solids or liquids?
Cis fatty acids usually exist as liquids at room temperature.
Why do cis fatty acids usually exist as liquids?
Cis fatty acids usually exist as liquids because they cannot pack closely together.
What do low density lipoproteins (LDLs) do?
LDLs are responsible for carrying cholesterol and triglycerides from the liver to the tissues.
What do high density lipoproteins (HDLs) do?
HDLs can remove cholesterol from the arteries and transport it back to the liver for excretion or re-utilisation.
What is amphetamine used for?
Amphetamine is used to treat daytime drowziness and chronic fatigue syndrome.
What is phenylephrine used for?
Phenylephrine is a decongestant.
What is adrenaline used for?
Adrenaline is the fight or flight hormone.
What is a primary amine?
A primary amine is one in which only one hydrocarbon chain attached to the nitrogen.
What is a secondary amine?
A secondary amine is one in which the nitrogen atom is attached to two carbon chains.
What is a tertiary amine?
A tertiary amine is one in which the nitrogen atom is attached to three carbon chains.
Amines are what? (acids, alkalis, bases)
Amines are weak bases.
What forms when an amine accepts a proton?
When an amine accepts a proton a dative covalent bond forms between the lone pair of the nitrogen and the proton.
How are aliphatic amines generated?
Aliphatic amines can be prepared by gently warming halogenoalkanes with an excess of ammonia using ethanol as the solvent.
How are nitrobenzene and other nitroarenes reduced?
Nitrobenzene and other nitroarenes can be reduced using a mixture of tin and concentrated HCl heated under reflux followed by neutralisation of the excess HCl.
What are the two steps in the industrial preparation of dyes?
Diazotisation and coupling reactions
