Amines, amides, amino acids and proteins Flashcards
Why can the ammonia molecule accept protons?
It has a lone pair of electrons
What are amines?
Compounds based on ammonia where one or more of the hydrogen atoms have been substituted for an alkyl or aryl group
How are amines formed?
Ammonia heated under pressure with halogenoalkane
What is a primary, secondary and tertiary amine?
Primary - 1 hydrogen replaced
Secondary - 2 hydrogen replaced
Tertiary - 3 hydrogen atoms replaced
How can a hydrogen atom on a primary or secondary amine be replaced?
Ethanoyl chloride or ethanoic anhydride
Substitues a CH3CO- group in
What does a n indicate in the naming of a substance?
Bonded to nitrogen atom
How are aryl amines formed?
Reduction of nitrobenzene using tin and concentrated HCl
How would aryl amines be formed in the lab?
Carried out under reflux
Flask is cooled and NaOH added to redissolve initial precipitate of Sn(OH)4
Water added and steam distillation used to separate phenylamine and water
Salting carried out (powdered NaCl added) and transferred into separating funnel
Ethoxyethane added and aequous layer run off and repeated
KOH pellets added to remove HCl and dry extract
Ethoxyethane is distilled off
What catalyst is used in industry to form phenylamine?
Iron rather than tin because it is cheaper
Why do teriary amines have lower metling and boiling temperatures than primary and secondary amines?
Hydrogen bonding possible in primary and secondary
Why are aryl amines only slightly soluble in water?
Aromatic nature of benzene ring outweighs tendancy of NH2 group to form hydrogen bonds
Are primary alkyl amines stronger or weaker bases than ammonia?
Stronger because electrons shift from the akyl group, increasing the electron density on the nitrogen atom so that it can hold a proton more strongly
Is phenylamine a stronger or weaker base than ammonia?
Weaker because the lone pair of electron on the nitrogen atom interacts with the pi electrons in the ring, reducing the electron density of the nitrogen atom
Must be a high exess of H+ form salt
Readily undergoes electrophilic substitution
How does an amine react with ethanoyl chloride?
Ethanoylation where one hydrogen atom in the nitrogen atom is exchanged for CH3CO-
HCl also formed
What is the mechanism for the ethanoylation of an mine?
1. Nitogen attracted to positive carbon Breaks bond with oxygen 2. Oxygen forms bond with carbon Carbon breaks bond with chlorine Nitrogen breaks bond with hydrogen
What simplifies the production of paracetamol?
Doesn’t produce chiral molecules
Normally considered at every stage
How is nitrous acid made?
Very unstable compound so must be made as needed and reactions must be kept below 5^C
NaNO2 + HCl –> NaCl + HNO2
What’s produced when nitrous acid reacts with a primary amine?
Alcohol
Nitrogen gas
Water
What happens when an aromatic amine reacts with nitrous acid above 5 degrees?
Alcohol eg phenol
Nitrogen gas
Water
What happens when an aromatic amine reacts with nitrous acid below 5 degrees?
Diazonium compound formed (benzene with N+=-NCl-)
2 water molecules
Why don’t aliphatic compounds produce diazonium salts?
So unstable
Additional stability results from the delocalised electrons of the benzene ring as it donates electron density from the ring
Why are the diazoniums so useful?
Benzene reacts with electrophiles but the diazonium group opens the benzene ring to attack by nucleophiles
How do you form phenol from a diazonium salt? What else is produced?
Steam distillation
Nitrogen gas
How do you form iodobenzene from a diazonium salt? What else is produced?
Reflux with KI
Nitrogen gas
How do you form bromobenzene from a diazonium salt? What else is produced?
Conc HBr
CuBr catalyst and reflux
Nitrogen gas
How do you form chlorobenzene from a diazonium salt? What else is produced?
Conc HCl
CuCl catalyst and reflux
Nitrogen gas
How do you form CNbenzene from a diazonium salt? What else is produced?
Conc HCN
CuCN catalyst and reflux
Nitrogen gas
What is the coupling reaction?
Benzendiazonium ion reacts readily in cold alkaline solution with aromatic amines and phenols
Join two aromatic rings together using -N=N-
HCl also produced
Why are the results of the coupling reactions coloured?
Extensive delocalisation electron systems that spread across the entire molecule through the N=N coupling
Used as colourfast dies
What are polyamides?
Joining amide molecules together in a condensation reaction
For example nylon
What does nylon 6,6 mean?
6 carbon atoms in each of the monomers
Hexandioic acid and 1,6-diaminohexane
How are the monomers obtained for nylon?
Phenol or cyclohexane
What is nylon used for?
Stockings
Wool and ropes to add resistance and wear and tear
What is produced in the condensation reaction when producing polyamides?
2 small molecules
Polyamide (C and N at ends of chains)
What are the properties of Kevlar?
Polyamide Resists high temperatures Low thermal conductivity High tensile strength Flame, chemical and cut resistant
What are the uses of Kevlar?
Replacement for steel in racing car tyres
Bullet proof vests
Data transmission cables
What can poly(propenamide) be used for?
Thickener and filler in facial surgery
Readily cross-linked with other chains, giving it a huge capacity to absorb water and making it useful for soft contact lenses
What is poly(propenamide)?
Addition polymer formed from 2-propenamide
How is poly(ethanol) produced?
Addition polymer manufactured from another polymer by the process of ester exchange
First, ethyl ethanoate is polymerised
Next, ester exchange reaction with methanol takes place by which can be controlled by altering the temperature
Methyl ethanoate is also produced
What does the solubility of the final polymer depend on when producing poly(ethanol)?
Percentage of ester groups that have been replaced
Eg can be made to allow it to dissolve in hot water which can be used. Infected sheets put into poly(ethanol) bag and dissolved in washing machine
How can a viscoelastic gel be formed?
When poly(ethanol) is reacted with Na2B4O7 dissolved in water Borate ions interact with OH group in the polymer and forms cross-links between the chains
What are the properties of polyamides?
Addition polymers (polyethene, polypropene) are resistant to chemicals such as acids, alkalis and organic solvents as the carbon and hydrogen atoms are not easily attacked Polyamides have links between the molecules which are vulnerable to attack under acidic or alkaline conditions
What is the displayed formula of a general amino acid?
R
H2N-C-COOH
H
R may be polar or non-polar
What role do amino acids play in the body?
Make up proteins which make up enzymes
Enzymes control body chemistry and cell structure
Tissues such as muscles are made up mainly from amino acids in the form of proteins
Every protein consists of a very long chain of amino acids in a particular sequence
Proteins you eat are broken down into amino acids by digestion in your body
How can an amino acid be represented?
3 letter short hand which is often the first 3 letters of the trivial name
What is a peptide bond?
When two amino acids join together, undergoing a condensation reaction (losing molecule of water) and forms a dipeptide
OH from COOH and H from NH2 react
What happens when amino acids are in alkaline solution?
Amino acid loses a proton from COOH and forms a negative ion
What happens when amino acids are in alkaline solution?
Amino acid receives a proton on NH2 group and forms a positive ion
What is a zwitterion?
Formed when an amino acid is in neutral solution
Both positive and negative ions within the same molecule
H from COOH is donated to NH2
Exist as zwitterions when in solid state, explaining relatively high melting temperatures and why they dissolve in water
