Nitrogen Compounds
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What constitutes an amine compound?
At least 1 nitrogen atom must be bonded to a carbon atom.
Why are amines basic?
Their nitrogen atom contains a lone pair of electrons This makes them H+/proton acceptors
Why are amines soluble?
They can form hydrogen bonds with water molecules.
What physical characteristics do solutions of amines show?
They are volatile liquids at RT with pungent smells.
Why are amines good nucleophiles?
They have a lone pair of electrons which means they are attracted to electron deficient centres (+ve charges)
How do we name primary amines?
Suffix ‘-ylamine’
How do we name secondary amines?
Using N- as the position indicator for substituent groups.
How do we name primary amines with -NH2 attached partway along a large carbon chain, as a substituent?
Positional indicator followed by amino- prefix
What product is formed when an amine reacts with an acid?
Amines are basic Thus this is an acid-base reaction A salt is formed with a +ve nitrogen atom
Why is the reaction between an amine and an acid NOT a neutralisation?
Though this is an acid-base reaction No water is formed Thus not neutralisation
Give an alternative name for an optical isomer.
Enantiomer.
What is an optical isomer?
Molecules that form non-superimposable mirror images of one another. Has a chiral centre.
What bond shape forms around a chiral centre?
Tetrahedral
What is chirality?
Molecules are chiral if 4 different groups are attached to a single carbon atom.
Give na example of a nitrogen compound that displays chirality.
Amino acids
What physical property dominates the reactions of amines?
Their lone pair
What type of reaction mechanism will an amine typically undergo?
Nucleophilic substitution.
Describe a mechanism for nucleophilic substitution.
2-step… RBr + NH3 -> RNH3+Br- RNH3+Br- + NaOH -> RNH2 + NaBr + H2O Ammonia must be dissolved in ethanol
Why is the nucleophilic substitution of ammonia a two step mechanism?
Addition of NaOH directly will result in the formation of an alcohol Since :OH- is a good nucleophile
Why does the nucleophilic substitution of ammonia not produce a pure product?
The nitrogen atom on the product still has a lone pair Further substitution can occur to form secondary, tertiary and quaternary amines
What constitutes an amino acid?
Amine and carboxylic acid group
What is an alpha amino acid?
NH2 is bonded to the second (alpha) carbon
What functional groups do amino acids have? How does this affect its properties?
-NH2 accepts protons so is basic - COOH donates protons so is weakly acidic (note reversible)
What is a zwitterion?
Double-charged species formed by amino acids where NH2 forms NH3+ and COOH forms COO- No overall charge but both ends are oppositely charged AT ISOELECTRIC POINT