F334 - what's in a medicine?

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F334 ­ What's in a Medicine?
Carboxylic Acids and their Derivatives
Carboxylic Acids:
Contain the carboxyl functional group.
Their systematic names all end with ­oic acid.
The formula is often shorted to ­COOH
When two carboxyl groups are present the ending ­dioc acid is used.
When naming branched chain carboxylic acids, the carboxyl carbon is assigned number 1.
Acid-Base Reactions:
Being weak acids, carboxylic acids partially dissociate in aqueous solution to form oxonium
ions (H3O+) and carboxylate ions (RCOO- ).
HCOOH(aq) + H2O(l) H3O+ HCOO-(aq)
Carboxylic acids react with bases to produce salts.
They are important chemically as many useful derivatives can be made from them.
CH3COOH(aq) + NaOH(aq) CH3COO-Na+(aq) + H2O(l)
Esterification Reactions:
Carboxylic acids react with alcohols in the presence of a strong acid catalyst
For example a few drops of concentrated sulphuric acid.
They also need to be heated under reflux.
This reaction is reversible and comes to equilibrium during refluxing.
Carboxylic acid + alcohol ester + water
CH3COOH(l) + CH3CH2OH(l) CH3COOCH2CH3(l) + H2O(l)
Ethanoic Acid + Ethanol Ethyl ethanoate + water
Tests for Carboxylic Acids:
Will react with carbonates to produce carbon dioxide.
Sodium carbonate or sodium hydrogencarbonate solutions are commonly used.
2CHOOH(aq) + Na2CO3(aq) 2HCOO-Na+(aq) + CO2(g) + H2O(l)
Methanoic acid + sodium carbonate Sodium methanoate + carbon dioxide + water
Will produce bubbles of carbon dioxide gas which are readily seen.
Carbon dioxide can be tested for as the gas will turn limewater milky/cloud.
Derivatives:
Esters, have the functional group ­COO
An example is methyl ethanoate, notice how the first part of the name refers to group
attached to the oxygen.
Acyl chlorides have the functional group ­ COCl

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An example would ethanoyl chloride.
Amides have the functional group ­CONH
An example would be ethanamide
Acid anhydrides are another derivative
An example would be Ethanoic anhydride
The OH Group in Alcohols, Phenols and Carboxylic Acids
The OH Group:
Can occur in three different environments ­ alcohols, phenols and carboxylic acids.
Alcohols contain the hydroxyl functional group attached to an aliphatic carbon chain.
Phenols are compounds that have one or more ­OH groups attached directly onto a benzene
ring.…read more

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When a neutral iron (iii) chloride solution is added to phenol or its derivatives, a purple
complex is formed.
This test allows us to distinguish between alcohols and phenols.
Acidic Properties:
Alcohols, phenols and carboxylic acids are all weak acids.…read more

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The other product of the reaction is water.
The reaction can be reversed and the ester can be hydrolysed.
In this case a more suitable catalyst would be dilute sulphuric acid.
Making esters from a phenol:
Do not form esters in the same way as alcohols.
Will react with acyl chlorides ( at room temperature) or acid anhydrides (heat under reflux) to
make esters.
In both cases, anhydrous conditions are essential.
Naming and Drawing Esters:
Named in two parts.…read more

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Therefore both reactions have a 100% atom economy.
Substitution reactions:
Involve replacing one group in a molecule with another.
There are always two products formed.
Therefore atom economy is always less than 100%.
The larger the Mr of the leaving group the lower the atom economy.
Elimination reactions:
Involved removing a group from a molecule.
One reactant molecule forms two product molecules.
Therefore atom economy will always be less than 100%.…read more

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The dichromate(VI) ion is reduced to Cr3+ in the reaction:
Cr2O72-(aq) + 14H+(aq) + 6e- 2Cr3+(aq) + 7H2O
Reactions:
Only aldehydes can be further oxidised with acidified potassium dichromate(VI) because of
the hydrogen atom on the carbonyl group.
They also react with Fehlings solution.
The aldehyde is oxidised to a carboxylic acid and the blue Cu2+ ions are reduced to Cu+ in
copper(I) oxide.
This forms an orange/brown precipitate.
Ketones are not oxidised by Fehling's Solution and so there is no colour change.…read more

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This is the Brnsted-Lowry theory.
Acids donate H+ to water in aqueous solution to become H3O+ (the oxonium ion)
An alkali is a base that dissolves in water to produce hydroxide ions
For example, sodium hydroxide, potassium hydroxide and sodium carbonate
Sodium carbonate produces hydroxide ions by the following reaction:
CO32-(aq) + H2O(l) HCO3-(aq) + OH-(aq)
Proton transfer:
In the reaction below a proton is transferred from HNO3 to H2O.
HNO3 is acting as an acid and H2O is acting as a base.…read more

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Indicators:
Acid-base indicators, such as methyl orange or phenolphthalein are themselves weak acids.
In order to behave as an indicator the conjugate acid and base forms of the molecule must
have different colours. In the case of methyl orange, the acid form is red and the conjugate
base is yellow.…read more

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Fragmentation
The molecular ion peak corresponds to the molecular mass of the compound being
analysed. It is the peak furthest to the right on the spectrum.
From the mass spectrum above, it is clearly evident that the ions which correspond to
the molecular ion (X+) are not the only ones reaching the detector.
This is because the other lines on the spectrum correspond to lighter ions that are the result
of fragmentation (breakdown of X+).…read more

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Eventually the masses that have been lost from a compound become familiar. For example,
28 is the loss of a C=O group, 77 for the loss of a C6H5 (benzene ring) etc.
Isotope Peaks:
Some elements have more than one naturally-occurring isotope. For example natural chlorine
consists of 75% 35Cl and 25% 37Cl.
So, what happens when a molecule containing chlorine is fragmented in the mass
spectrometer? Well, there are two sorts of ions, one containing 35Cl and the other
containing 37Cl.…read more

Comments

Iyanu

Very useful, thank you for the time and effort

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