Chemistry Unit 6 Amines (Ch27)

What is an amine? (1)

A compound containing -NH2 group.

How do you name amines if the substituent groups aren't the same?

As an N-substituted derivative of the longest carbon chain. Eg, N-ethylpropylamine:

What do amines primarily react as? Why? (2)

Bases. (1) There is a lone pair of e- on the N atom which is able to accept protons. (1)

How are primary amines formed? (with reactants, conditions, and equations) (4)

★ Reactants: haloalkane and ammonia.
★ Conditions: excess ammonia (to prevent further substitution maximising no. of primary amines) and ethanol as solvent (preventing hydrolysis of haloalkanes).
Equations:
* CH3CH2Br + NH3 -> CH3CH2NH3+Br-
* CH3CH2NH3+Br- + NaOH ⇌ CH3CH2NH2 + NaBr + H2O

How are secondary and tertiary aliphatic amines formed? (with reactants, conditions, and equations) (3)

* Reactants: haloalkane and primary/secondary amine.
* Conditions: ethanol as solvent (preventing hydrolysis of haloalkanes).
* Equations:
R1NH2 + R2Cl -> R1(R2)NH2+Cl-
R1(R2)NH2+Cl + NaOH -> R1R2NH2 + NaOH + H2O

What are the reactants + conditions of the formation of primary amines? Explain why the conditions are so. (4)

★ Reactants: haloalkane and ammonia.
★ Conditions: excess ammonia and ethanol as solvent
* excess ammonia prevents further substitution maximising no. of primary amines
* ethanol as solvent prevents hydrolysis of haloalkanes

What are the equations of forming primary amines? (using a bromoalkane) (2)

* CH3CH2Br + NH3 -> CH3CH2NH3+Br-
* CH3CH2NH3+Br- + NaOH ⇌ CH3CH2NH2 + NaBr + H2O

What are the conditions + reactants of phenylamine formation from nitrobenzene? What type of reaction is it? (3)

Conditions: reflux.
Reactants:
* Sn
* conc. HCl
* excess NaOH (required for hydroxide ions).
Type of reaction: reduction

What is the balanced equation for conversion of nitrobenzene into phenylamine? with conditions and reactants labelled. (5)

* nitrobenzene + 6[H] -> phenylamine + water
* Conditions: reflux.
Reactants:
* Sn
* conc. HCl
* excess NaOH (required for hydroxide ions).

Show the two steps involved in the conversion of nitrobenzene into phenylamine. (2)

Write an equation to show how methylamine is able to behave as a base.

propylamine + hydrochloric acid

RNH2 + HCl ->

RNH2 + HCl --> RNH3+Cl- (makes a salt)

What does ammonia act as in a reaction with a haloalkane? (2)

acts as a nucleophile (1) in a nucleophilic substitution reaction (1) with a haloalkane.

Why is excess ammonia used in preparation of primary amines? (1)

it prevents further substitution of the amine to make tertiary and secondary amines.

What are the two steps of forming a primary amine? Don't include equations. (2)

1. formation of a salt
2. formation of amine

What are the two steps of forming a primary amine? Include equations. (2)

1. RCl + NH3 ->RNH3+Cl- (makes a salt)
2. RNH3+Cl + NaOH -> RNH2 + NaCl + H2O

Why is NaOH required in forming a primary amine? (1)

provides hydroxide ions

Give equations that show how secondary and tertiary amines are formed. (3)

* R1NH2 + R2Cl -> R1(R2)NH2+Cl-
* R1(R2)NH2+Cl + NaOH -> R1R2NH2 + NaOH + H2O

How do amino acids react with acids? Give an equation where an amino acid reacts with HCl. (1)

amino acid + acid -> carboxylate salt w/ a positive charge on NH3 + ion from acid (see image)

How do amino acids react with aqueous alkalis? Give an equation where an amino acid reacts with NaOH. (1)

forms a carboxylate salt with ions on the non-double bond O- (Na+)
AND water

How do amino acids react with alcohols? Give an example equation with all reactants and products. (3)

* reactants: alcohol AND H+ ion
* they form esters AND water
* the NH3+ is positively charged

What are amides? (1)

A compound containing a -CONH2 group.

What are optical isomers? (1)

Stereoisomers that are non-superimposable mirror images.

What is required for two molecules to be optical isomers? (2)

* must be stereoisomers that are non-superimposable mirror images.
* must have 4 different groups attached to a carbon (called the chiral centre)

What are amino acids? (1)

A central carbon with an amino group and carboxyl group.

What is a chiral centre? (1)

A carbon atom with four different atoms or groups attached to it

How do you know something is an α amino acid? (1)

* its -NH2 and -COOH groups are attached to the same C atom

What is the general formula of amino acids?

RCH(NH2)COOH

Show what aminoethanoic acid looks like

CH3CH(NH2)COOH

What are the conditions required for amino acid reactions with alcohol, how is this shown? Why? (3)

* HEAT
* with alcohol in the presence of H2SO4
* acidic conditions shown by a H+ as a REACTANT
* to protonate the basic amine group of the ester formed

Which is the only α amino acid with no chiral centre? Why? (2)

Glycine (1) since it has 2 H atoms attached to it and chiral centres have 4 DIFFERENT atoms/groups of atoms attached. (1)

How to calculate the number of isomers of a molecule with more than one chiral centre? (2)

* 2^n
* where n is the number of chiral atoms

How are optical isomers drawn?

Glutamic acid and glycine are both α amino acids. Glutamic acid exists as two optical isomers, but glycine does not. Explain what structural feature causes optical isomerism in organic molecules. Use appropriate diagrams and these two amino aids to illustrate your answer. (5)

* glutamic acid is chiral (1)
* because it has four different group attached to a carbon. (1)
* the mirror images of these are non-superimposable (1)
* eg: diagram (1)
* glycine doesn't have optical isomers because the central carbon is not attached to four different groups (1)

See the diagram of geraniol opposite. Name the type of stereoisomerism shown by geraniol. (1)

cis/trans

State how cis/trans stereoisomerism arises in organic molecules (1)

the double bond does not rotate.

Look at the diagram of geraniol opposite. Explain why one of the double bonds in geraniol does not give rise to stereoisomerism. (1)

it needs different groups attached to each C of the C=C (1)

How are primary amides converted to carboxylic acids? (reagents, type of reaction, give an example equation) (3)

Reagents: HCl (aq)
Type of reaction: acid hydrolysis
Equation: CH3CONH2 + H2O + HCl → CH3COOH + NH4+Cl-

How are primary amides formed? What precaution must be taken? (2)

* By reacting acyl chlorides with ammonia.
* You require a lot of NH3 to react with HCl to allow the reaction to go to completion.

Give the mechanism for the formation of primary amides from acyl chlorides and ammonia.

What are the 2 types of polymerisation?

Addition polymerisation.
Condensation polymerisation.

What is addition polymerisation? (1)

When unsaturated monomers react.

What is condensation polymerisation? (3)

* Two different monomers that add together (1) with a small molecule usually given off as a side-product [1] (eg, H2O or HCl).
* These monomers usually have the same functional group on both ends of the molecule (eg, diamine, dicarboxylic acid, dioil, diacyl chloride). (1)

Give the 2 most common types of condensation polymers with their linkage. (3)

* Poly(esters) which contain an ester link (-COO-).
* Poly(amides) which contain an amide link (-CONH-).
* They form what is called an ester linkage or amide linkage.

How and why are polyester and polyamides biodegradable? (2)

They can be broken down by hydrolysis. (1) Due to their polar nature attracting attacking species. (1)

Why may condensation polymers be photodegradable? (1)

As the C=O bond absorbs radiation.

What are condensation polymers hydrolysed by? In what is each hydrolysed more easily? (3)

* Hot (aq) acid or alkali.
* Poly(amides) are hydrolysed more easily with strong acid.
* Poly(esters) are hydrolysed more easily with strong bases.
(It can be hydrolysed by water but it's FAR too slow.)

What does the base and acid hydrolysis of poly(esters) yield?

Base - dicarboxylate salt and diol. / Acid - dicarboxylic acid and diol.

What does the base and acid hydrolysis of poly(amides) yield?

Base - dicarboxylate salt and diamine. / Acid - dicarboxylic acid and diammonium.

What is the difference between condensation polymers and addition polymers? (4)

The backbone of an addition polymer will be made of carbon atoms (1) and its monomer contains C=C (1) whereas a condensation polymer will contain ester or amide linkages (1) and will wither have monomers with one monomer with two functional group or two monomers with different functional groups. (1)

Explain why certain amino acids are described as α-amino acids. (1)

If there is both an amine -NH2 and carboxyl -COOH group attached to the same carbon. (1)

Explain what is meant by the term condensation polymer. (1)

monomers which join with the loss of a small molecule, usually H2O or HCl

State the reagents and conditions for synthesis of H2N(CH2)4NH2 from Cl(CH2)4Cl. (2)

excess ammonia (1) and ethanol solvent (1)

C2H5NH2 + CH3COOH makes which salt?

(C2H5NH3+)(CH3COO-)