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.