What's in a Medicine
28 May 2024 14:47
WM1 Development of ideas on medicine and alcohols.
Properties of Alcohols Dehydration of alcohols and other reactions
Alcohols are polar due to the polarised O-H bond, so alcohols experience hydrogen bonding which are Alcohols can lose a molecule of water to from an alkene, this requires a heated aluminium oxide
the strongest intermolecular force. This is why alcohols have higher boiling points than their catalyst Al2O3 at 300 degrees C or heated under reflux with concentrated sulfuric acid.
corresponding alkanes with similar relative molecular masses. Hydrogen bonding also explains why
alcohol and water mix; the longer the hydrocarbon chain then the less important the -OH properties are
so the solubility decreases, so their properties become more like their corresponding alkane.
There are three types of alcohol: primary, secondary, and tertiary which all depends on the position of
the OH group.
Dehydration reactions are examples of elimination reactions, alcohols can also undergo substitution
Type of alcohol Position of OH Example
reactions. They will react with halide ions in the presence of a strong acid to produce haloalkanes in
Primary The carbon the OH is bonded to bonds to one other carbon Butan-1-ol nucleophilic substitution.
Secondary The carbon the OH is bonded to bonds to two other carbons Butan-2-ol
Tertiary The carbon the OH is bonded to bonds to three other carbons 2-methylpropan-2-ol Esterification
Esters can be formed with either an acid anhydride or carboxylic acid. Esterification is the process of
Oxidation of alcohols making an ester with a carboxylic acid. Esterification reactions occur very slowly without a catalyst so
concentrated sulphuric acid is used and the reaction is heated under reflux, it is a reversible reaction
The -OH group can be oxidised by strong oxidising agent such as acidified potassium dichromate (VI). that comes to equilibrium so there is a mixture of products and reactants and therefore the ester
The solution starts orange due to the dichromate(VI) ion, Cr2O72-(aq) and when its reduced it turns into must be separated, distilled, and purified. Esters are names with the alcohol first and then the
green chromate (III) ions, Cr3+(aq). This shows that the alcohol has been reduces and the O-H is reduced carboxylic acid last.
to C=O. Oxidation of alcohols will not happen unless there is a hydrogen atom on the carbon that the
OH is bonded to. The product is either an aldehyde or ketone depending on the type of alcohol and
conditions in the reaction.
Primary alcohols are initially oxidised to aldehydes when acid is in excess and not heated under reflux.
Acid anhydrides are more reactive than carboxylic acids and react completely with an alcohol when
They can also be (further) oxidised to a carboxylic acid when the oxidising agent is in excess and
warmed which produces a much higher yield. The products are an ester and a carboxylic acid.
heated under reflux. Secondary alcohols oxidise to make ketones when heated under reflux and in the
presence of an oxidising agent, they cannot be further oxidised as that would involve breaking a very
strong covalent bond. Tertiary alcohols do not oxidise at all as there is no hydrogen atom bonded to
the carbon that the OH group is bonded to. Heating under refulx reduces any reactants lost and is
safe for heating volatile or flammable liquids
Ethers and Purification
Aldehydes have a carbonyl group, C=O, at the end of the alkane chain. Ketones have the carbonyl group
within the alkane chain. Ethers are structural isomers of alcohols with the
general formula R-O-R for example:
Aldehyde Most common haloalkanes, esters and ethers or organic liquids, during synthesis only a crude
Ketone product is made so it must be purified before it can be used either by a separating funnel, drying
agents, or simple distillation.
WM2 The -OH group in different environments and derivatives of carboxylic acids
Carboxylic acids and phenols
Carboxylic acids have a carboxyl group -COOH but without the two oxygens bonded together. The -OH
Iron (III) chloride testing
group in this can be replaced by other groups to give derivatives of carboxylic acids. It can occur in three
different environments in organic molecules: as part of -COOH in carboxylic acids, attached to an alkane Some atom groupings become attached to metal ions and form complexes, only phenols have the
chain in alcohols, or attached to a benzene ring in phenols. Phenols look similar to alcohols but behave right arrangement of atoms to form a purple complex with Fe3+ in neutral solution, so they are the
differently as they have an aromatic ring. only ones to turn purple with neutral iron (III) chloride solution.
Acidic properties of the -OH group
Forming esters
The -OH group reacts with water, water dissociates to a very small extents so at any one time some water
molecules donate H+ and becomes a weak acid. A similar reaction happens with ethanol, but less and the Phenols can react with acid anhydrides to form esters and carboxylic acids react with an alc0hol.
equilibrium lies further left so ethanol is a weaker acid than water. With phenols, the equilibrium lies more
right so phenol is more acidic than water but still weak. Esterifying the phenol of 2-ethanoyloxybenzoice acid gives aspirin and is quite soluble in water so can
be absorbed into the bloodstream
ethanol < water < phenol < carboxylic acid Esterifying it with methanol gives methyl 2-hydroxybenzoate also known as oil of wintergreen and is
In order of acidic strength:
soluble in fats and oils.
Phenols and carboxylic acids are strong enough acids to react with strong bases (NaOH) to form salts. The
salts produced are ionic and stay in solution. Only carboxylic acids have a strong enough concentration of H+
ions to produce carbon dioxide gas with carbonates, they will make carbonates fizz but alcohols and phenols
do not.
WM3 Infrared spectroscopy
Energy in molecules is quantised, in infrared spectroscopy a substance is exposed to radiation which makes vibrational changes occur in the molecule, which
absorb infrared radiation of specific frequencies.
Speed of light (3.00 x 108) = wavelength x frequency
The frequencies of the absorptions are different for each molecules because the energy needed to excite a vibration depends on the strength of the bond, the
weaker the bond the less energy required. In more complex molecules more bond deformations are possible that in volved more than two atoms, or there a re
different vibrational modes/behaviours which also contain bonds with different enthalpies.
The infrared spectrometer detects absorptions and produces an infrared spectrum, if there has been an absorption of radiation the % transmittance will drop and it will produce a trough in the spectrum at a specific frequency
that will correspond to a bond within the molecule. Below 1500 cm-1 is more complex and characteristic cot the molecule, so it is called the fingerprint region, it is used for final identification and can be compared next to
established spectra.
In an exam, the wavenumbers are given to you and to state an appearance you must say there is absorption at 'wavenumber' which is due to 'corresponding bond'
WM4 Mass spectrometry
Mass spectrometry can be used to find out the atomic masses of elements and relative abundances of isotopes in an element, for more complex molecules they are fragmented, ionised and detected.
Chemistry Page 1
28 May 2024 14:47
WM1 Development of ideas on medicine and alcohols.
Properties of Alcohols Dehydration of alcohols and other reactions
Alcohols are polar due to the polarised O-H bond, so alcohols experience hydrogen bonding which are Alcohols can lose a molecule of water to from an alkene, this requires a heated aluminium oxide
the strongest intermolecular force. This is why alcohols have higher boiling points than their catalyst Al2O3 at 300 degrees C or heated under reflux with concentrated sulfuric acid.
corresponding alkanes with similar relative molecular masses. Hydrogen bonding also explains why
alcohol and water mix; the longer the hydrocarbon chain then the less important the -OH properties are
so the solubility decreases, so their properties become more like their corresponding alkane.
There are three types of alcohol: primary, secondary, and tertiary which all depends on the position of
the OH group.
Dehydration reactions are examples of elimination reactions, alcohols can also undergo substitution
Type of alcohol Position of OH Example
reactions. They will react with halide ions in the presence of a strong acid to produce haloalkanes in
Primary The carbon the OH is bonded to bonds to one other carbon Butan-1-ol nucleophilic substitution.
Secondary The carbon the OH is bonded to bonds to two other carbons Butan-2-ol
Tertiary The carbon the OH is bonded to bonds to three other carbons 2-methylpropan-2-ol Esterification
Esters can be formed with either an acid anhydride or carboxylic acid. Esterification is the process of
Oxidation of alcohols making an ester with a carboxylic acid. Esterification reactions occur very slowly without a catalyst so
concentrated sulphuric acid is used and the reaction is heated under reflux, it is a reversible reaction
The -OH group can be oxidised by strong oxidising agent such as acidified potassium dichromate (VI). that comes to equilibrium so there is a mixture of products and reactants and therefore the ester
The solution starts orange due to the dichromate(VI) ion, Cr2O72-(aq) and when its reduced it turns into must be separated, distilled, and purified. Esters are names with the alcohol first and then the
green chromate (III) ions, Cr3+(aq). This shows that the alcohol has been reduces and the O-H is reduced carboxylic acid last.
to C=O. Oxidation of alcohols will not happen unless there is a hydrogen atom on the carbon that the
OH is bonded to. The product is either an aldehyde or ketone depending on the type of alcohol and
conditions in the reaction.
Primary alcohols are initially oxidised to aldehydes when acid is in excess and not heated under reflux.
Acid anhydrides are more reactive than carboxylic acids and react completely with an alcohol when
They can also be (further) oxidised to a carboxylic acid when the oxidising agent is in excess and
warmed which produces a much higher yield. The products are an ester and a carboxylic acid.
heated under reflux. Secondary alcohols oxidise to make ketones when heated under reflux and in the
presence of an oxidising agent, they cannot be further oxidised as that would involve breaking a very
strong covalent bond. Tertiary alcohols do not oxidise at all as there is no hydrogen atom bonded to
the carbon that the OH group is bonded to. Heating under refulx reduces any reactants lost and is
safe for heating volatile or flammable liquids
Ethers and Purification
Aldehydes have a carbonyl group, C=O, at the end of the alkane chain. Ketones have the carbonyl group
within the alkane chain. Ethers are structural isomers of alcohols with the
general formula R-O-R for example:
Aldehyde Most common haloalkanes, esters and ethers or organic liquids, during synthesis only a crude
Ketone product is made so it must be purified before it can be used either by a separating funnel, drying
agents, or simple distillation.
WM2 The -OH group in different environments and derivatives of carboxylic acids
Carboxylic acids and phenols
Carboxylic acids have a carboxyl group -COOH but without the two oxygens bonded together. The -OH
Iron (III) chloride testing
group in this can be replaced by other groups to give derivatives of carboxylic acids. It can occur in three
different environments in organic molecules: as part of -COOH in carboxylic acids, attached to an alkane Some atom groupings become attached to metal ions and form complexes, only phenols have the
chain in alcohols, or attached to a benzene ring in phenols. Phenols look similar to alcohols but behave right arrangement of atoms to form a purple complex with Fe3+ in neutral solution, so they are the
differently as they have an aromatic ring. only ones to turn purple with neutral iron (III) chloride solution.
Acidic properties of the -OH group
Forming esters
The -OH group reacts with water, water dissociates to a very small extents so at any one time some water
molecules donate H+ and becomes a weak acid. A similar reaction happens with ethanol, but less and the Phenols can react with acid anhydrides to form esters and carboxylic acids react with an alc0hol.
equilibrium lies further left so ethanol is a weaker acid than water. With phenols, the equilibrium lies more
right so phenol is more acidic than water but still weak. Esterifying the phenol of 2-ethanoyloxybenzoice acid gives aspirin and is quite soluble in water so can
be absorbed into the bloodstream
ethanol < water < phenol < carboxylic acid Esterifying it with methanol gives methyl 2-hydroxybenzoate also known as oil of wintergreen and is
In order of acidic strength:
soluble in fats and oils.
Phenols and carboxylic acids are strong enough acids to react with strong bases (NaOH) to form salts. The
salts produced are ionic and stay in solution. Only carboxylic acids have a strong enough concentration of H+
ions to produce carbon dioxide gas with carbonates, they will make carbonates fizz but alcohols and phenols
do not.
WM3 Infrared spectroscopy
Energy in molecules is quantised, in infrared spectroscopy a substance is exposed to radiation which makes vibrational changes occur in the molecule, which
absorb infrared radiation of specific frequencies.
Speed of light (3.00 x 108) = wavelength x frequency
The frequencies of the absorptions are different for each molecules because the energy needed to excite a vibration depends on the strength of the bond, the
weaker the bond the less energy required. In more complex molecules more bond deformations are possible that in volved more than two atoms, or there a re
different vibrational modes/behaviours which also contain bonds with different enthalpies.
The infrared spectrometer detects absorptions and produces an infrared spectrum, if there has been an absorption of radiation the % transmittance will drop and it will produce a trough in the spectrum at a specific frequency
that will correspond to a bond within the molecule. Below 1500 cm-1 is more complex and characteristic cot the molecule, so it is called the fingerprint region, it is used for final identification and can be compared next to
established spectra.
In an exam, the wavenumbers are given to you and to state an appearance you must say there is absorption at 'wavenumber' which is due to 'corresponding bond'
WM4 Mass spectrometry
Mass spectrometry can be used to find out the atomic masses of elements and relative abundances of isotopes in an element, for more complex molecules they are fragmented, ionised and detected.
Chemistry Page 1
