18- Arenes, Amines, Amides, Amino acids, proteins, organic synthesis Flashcards
What is an amine?
A nitrogen compound where one or more of the hydrogen compounds in ammonia have been replaced by alkyl or aryl groups.
Name this compound: H2NCH2CH2NH2
1,2-diaminoethane
What is an amide?
Nitrogen compounds where the OH group of a carboxylic acid is replaced by an NH2 group.
What state are methyl and ethyl amine at room temperature?
Gases
What state are propyl and butyl amine at room temperature?
Liquid
What do methyl and ethyl amines smell like?
Fishy smelling ammonia.
Do alkyl amines dissolve in water and why?
Yes, as the Nitrogen in the amine group can hydrogen bond with the water.
Are amines bronsted-lowry bases or acids and why?
Bases, as the lone pair of electrons on the nitrogen act as a proton/H+ acceptor.
Why are alkyl amines stronger bases than ammonia?
The alkyl group is “electron releasing” and increase the electron density around the lone pair on the Nitrogen, making the attraction to the H+/proton stronger.
Why is phenylamine a much weaker base than ammonia?
The electron lone pair on the nitrogen is delocalised into the pi cloud of the benzene ring.
Describe Kekules model for benzene.
Ring of 6 carbons each with a hydrogen bonded to them. The double bond switches rapidly between the carbons.
Describe the delocalised model of benzene.
Bonds are all the same length (longer than double bonds but shorter than single bonds). Electrons form a ring of delocalisation.
Why are benzene rings alot less reactive than alkenes?
In alkenes, the electrons are concentrated in a double bond. In benzene rings, the delocalised electron ring means there is a much lower electron density, so electrophilic addition is alot less common in benzene compared to alkenes. Arenes instead tend to undergo electrophilic substitution.
Explain the enthalpy data suggesting benzene isn’t made of 3 double bonds.
You would expect the enthalpy change of hydration of benzene to be roughly 3 times that of cyclohexene to cyclohexane. However, it is actually alot less negative, suggesting benzene is alot more stable and doesnt just have 3 regular double bonds.
Equation and conditions for electrophilic substitution of Bromine with benzene.
FeBr3 or Fe heated, forming Bromobenzene and hydrogen bromide.
Equation and conditions for electrophilic substitution of Chlorine with benzene.
FeBr3 (or FeCl3) or Fe heated, forming Chlorobenzene and hydrogen Chloride.
Reagents for the formation of nitrobenzene from benzene?
HNO3 (nitric acid) in a concentrated H2SO4 catalyst. At 55 degrees C.
Show the equations for formation of the nitronium ion, NO2 +
HNO3 + H2SO4 -> H2NO3 + + HSO4 -
H2NO3+ -> H20 + NO2 +
What is a Friedel-Crafts reaction?
An electrophilic substitution reaction where a hydrogen atom in an arene is replaced by an alkyl or acyl group following attack by a carbocation or acylium ion electrophile.
Reagents and conditions for the alkylation of benzene? what side product is formed
R-Cl in AlCl3 in heat. HCl also formed.
Reagents and conditions for the acylation of benzene? what side product is formed.
R-COCl in AlCl3 in heat. HCl also formed.
Reagents and conditions for the addition of hydrogen to Benzene?
3H2 in Raney Nickel catalyst at 200 degrees C.
Why is Raney Nickel used as the catalyst in the addition of hydrogen to benzene instead of regular nickel?
Has greater surface area meaning more reactive sights are available for the reactants on the surface of the catalyst.
What state is Phenol at room temp?
Solid
Reaction of phenol in NaOH?
[()]-OH + NaOH -> [()]-ONa + H2O
Why is Phenol more reactive than Benzene?
The lone pair on the oxygen in the OH group interacts with the delocalised electron ring. These electrons are released into the ring, increasing it’s electron density and therefore making it more susceptible to electrophilic attack.
Reaction of Phenol and Bromine (aq)?
2,4,6-Tribromophenol (solid) and 3HBr (aq) are formed.
Reaction of Phenol and Nitric acid?
2 {()}-OH + 2HNO3 -> 2( O2N-{()}-OH ) +2H2O
Forms both 2 and 4 substituted Nitronium groups.
Reaction of amines with halogenoalkanes?
amine acts as nucleophile and attacks the electron poor (delta positive) carbon in the haloalkane. Halogen ion is released. Amine is formed.
Reaction of amine with acyl chloride?
nucleophilic attack leads to N- substituded amide
