alcohols

• Alcohols have the ending -ol and if necessary the position number for the OH group is added between the name stem and the –ol.
• If the compound has an –OH group in addition to other functional groups that need a suffix ending then the OH can be named with the prefix hydroxy.
• If there are two or more -OH groups then di, tri are used.
• Pressure can change the boiling point of a liquid.
• To get a correct measure of boiling point the thermometer should be above the level of the surface of the boiling liquid and be measuring the temperature of the saturated vapour.
• Measuring boiling point is not the most accurate method of identifying a substance as several substances may have the same boiling point.
• The H-O- C bond in alcohols is 104.5o (bent line shape), because there are 2 bond pairs of electrons and 2 lone pairs repelling to a position of minimum repulsion.
• All the H-C-H bonds and C- C-O in alcohols are 109.5o (tetrahedral shape), because there are 4 bond pairs of electrons repelling to a position of minimum repulsion.
• Alcohols combust with a clean flame.
• Sodium reacts with alcohols, this reaction can be used as a test for alcohols.
• Various halogenating compounds can be used to substitute the –OH group for a halogen.
• PCl5 (phosphorous(V)chloride) can be used as a test for alcohols, you would observe misty fumes of HCl produced.
• For Br use KBr, 50% concentrated H2SO4 to produce HBr.
• The phosphorous (III) Iodide is produced in situ by reacting red phosphorus and Iodine.
• Potassium dichromate K2Cr2O7 is an oxidising agent that causes alcohols to oxidise, the exact reaction depends on the type of alcohol, i.e. whether it is primary, secondary, or tertiary, and on the conditions.
• In the partial oxidation of primary alcohols, the orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion.
• In the full oxidation of primary alcohols, the orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion.
• In the oxidation of secondary alcohols, if the ketone has 5C’s or more in a chain then it needs a number to show the position of the double bond.
• There is no further oxidation of the ketone under these conditions.
• Reflux is used when heating organic reaction mixtures for long periods, with the condenser preventing organic vapours from escaping by condensing them back to liquids.
• Distillation is generally used as a separation technique to separate an organic product from its reacting mixture, and the distillate of the approximate boiling point range of the desired liquid needs to be collected.
• The liquid is carefully decanted into the distillation flask and distilled to collect pure product.
• The organic layer is then run into a clean, dry conical flask and three spatula loads of drying agent (anhydrous sodium sulfate) are added to dry the organic liquid.
• The drying agent should be insoluble in the organic liquid and not react with the organic liquid.
• The fact that aldehydes can be further oxidised to carboxylic acids whereas ketones cannot be further oxidised is the chemical basis for tests that are commonly used to distinguish between aldehydes and ketones.
• Sodium hydrogencarbonate will neutralise any remaining reactant acid and sodium chloride will help separate the organic layer from the aqueous layer.
• Purity of liquid can be determined by measuring a boiling point, which can be done in a distillation set up or by simply boiling a tube of the sample in an heating oil bath.
• The presence of a carboxylic acid can be tested by addition of sodium carbonate, which will fizz and produce carbon dioxide.
• Anti-bumping granules are added to the flask in both distillation and reflux to prevent vigorous, uneven boiling by making small bubbles form instead of large bubbles.
• Purifying an organic liquid involves putting the distillate of impure product into a separating funnel, washing product by adding either sodium hydrogencarbonate solution, shaking and releasing the pressure from CO2 produced, and then allowing the layers to separate in the funnel, and running and discarding the aqueous layer.
• Solvent extraction involves mixing organic solvent and oil-water mixture in a separating funnel, then separating the oil layer, distilling to separate oil from organic solvent, and adding anhydrous CaCl2 to clove oil to dry oil.
• Some 2 o and 3 o alcohols can give more than one product, when the double bond forms between different carbon atoms.
• Tertiary alcohols cannot be oxidised at all by potassium dichromate because there is no hydrogen atom bonded to the carbon with the OH group.