More Organic Chemistry Flashcards
If one hydrogen is replaced with an organic group you get a…
Primary amine
If 2 replaced = secondary amine
If 3 replaced = tertiary amine
If 4 replaced = quaternary ammonium ion
Amines are organic derivatives of…
Ammonia
Quaternary ammonium salts are used as….
cationic surfactants. These are things like fabric conditioners and hair products. They are quaternary ammonium salts with at least 1 long hydrocarbon chain. The positively charged part (ammonium ion) will bind to negatively charged surfaces such as hair and fibre-gets rid of static
An amine has a lone pair of electrons that can form ……
Dative covalent bonds
Explain how amines can form dative covalent bonds
Amines act as bases because they accept protons. Is a lone pair of electrons on the nitrogen atom that forms a dative covalent bond with the H+ ion. The strength of the base depends on how available the nitrogens lone pair of electrons is. The more available- the more likely the amine is to accept a proton and the stronger a base it will be. A lone pair of electrons will be more available if it’s electron density is higher. Primary aliphatic amines are stronger bases than ammonia, which is a stronger base than aromatic amines
Aliphatic amines are made from…
Haloalkanes or nitriles
How can aliphatic amines be made from haloalkanes
Heat a haloalkane with excess ammonia. End up with mixture of primary, secondary and tertiary amines and quaternary ammonium salts as more than one hydrogen is likely to be substituted. Can separate products using fractional distillation. Mechanism is nucleophilic substitution. As long as there is more of the haloalkane further substitutions can take place, end up with quaternary ammonium salt which can’t react further as it has no electrons
How can aliphatic amines be made from a nitrile
Reduce a nitrile to an amine using lithium aluminium hydride (LiAlH4), a strong reducing agent, followed by dilute acid. Another way is to reflux with sodium metal and ethanol. Industry use metal catalyst such as platinum or nickel at high temp and pressure (called catalytic hydrogenation)
Disadvantage of the process of making aliphatic amines from nitriles
LiAlH4 and sodium are too expensive for industrial use
What are amino acids made from
A basic amino group and an acidic carboxyl group
Amino acids info
Made from basic amino group and an acidic carboxyl group. Makes them amphoteric (got acidic and basic properties). They’re chiral molecules as the carbon has 4 different groups attached. So a solution of a single amino acid enantiomer will rotate polarised light
What is a zwitterion
A dipolar ion, it has both a positive and negative charge in different parts of the molecule. They only exist near an amino acids isoelectric point. This is the pH where the average overall charge on the amino acid is zero. It’s different for different amino acids, it depends on their R-group
What are proteins
Made up of lots of amino acids joined together by peptide links. The chain is put together by condensation reactions and broken apart by hydrolysis reactions
How do you break up proteins
Hot aqueous 6M hydrochloric acid is added and the mixture heated under reflux for 24 hours. Final mixture is then neutralised
How are addition polymers formed
The double bonds in alkenes can open up and join together to make long chains. The individual small alkenes are called monomers
What is condensation polymerisation
It usually involves 2 different types of monomer. Each monomer has at least 2 functional groups. Each functional group reacts with a group on another monomer to form a link, creating polymer chains. Each time a link is formed, a water molecule is lost. Examples of condensation polymers include polyamides, polyesters, polypeptides
When asked to make one compound from another you should make sure to include what?
Any special procedures eg refluxing
Conditions needed
Any safety precautions
How can you test whether you have a primary, secondary or tertiary alcohol
Warm it with the oxidising agent acidified potassium dichromate then watch for colour change
PRIMARY- the orange dichromate slowly turns green as aldehyde forms (then eventually carboxylic acid)
SECONDARY- orange dichromate slowly turns green as ketone forms
TERTIARY- nothing happens
How can you test to distinguish between an aldehyde and a ketone
Use Tollens reagent. Aldehyde forms silver mirror, no reaction with ketone
Could also use Fehlings solution or Benedicts solution, an aldehyde gives brick red precipitate, no reaction with ketone
Bromine can be used to test for….
Unsaturation
Shake compound with orange bromine solution. Solution will decolourise if substance is unsaturated
Explain why polyamides can be made into fibres suitable for use in weaving and sewing whereas polyalkenes prodcude fibres which are too weak for this process
Polyamides contain hydrogen bonds. In polyalkenes there are van der waal forces which are weak. There are therefore stronger forces of attraction in polyamides as hydrogen bonds are stronger
Why do poly(amides) have higher melting points than poly(esters)
Due to the hydrogen bonds
Hydrogen bonds are stronger than the vdw forces in the poly(ester)
Why does benzene not react with ammonia under normal conditions
Electron rich ring repels the nucleophile (ammonia)
Name the type of reaction between polyester and NaOH. explain why they react
Hydrolysis OR nucleophilic addition-elimination
The positive charge on the carbon reacts with the OH-
