Chapter 14 Alcohols
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What is an alcohol?
An organic compound which contains a hydroxyl group
What is the general formula for a non cyclic alcohol?
CnH2n+1OH
Why do alcohols have higher boiling points than Alkanes of the same chain length?
Alcohols are polar molecules, which can form hydrogen bonds between molecules. More energy is needed to overcome these hydrogen bonds than the sole weaker London forces of Alkanes, giving Alcohols higher boiling points
Why do very large alkanes and alcohols have similar boiling points?
The contribution of the hydroxyl group of the alcohol decreases as the chain length increases
Why are alcohols soluble in water?
The alcohol molecules are polar, and are able to form hydrogen bonds between the water and alcohol
Why does the solubility of alcohols decrease as they get larger?
The contribution of the hydroxyl group decreases as chain length increases. The proportion of hydrogen bonds form compared to the size of the molecule decreases
How are alcohols classified?
Primary- Carbon attached to the hydroxyl is also attached to at least 2 hydrogens, 1 R group Secondary- Carbon attached to the hydroxyl is attached to 1 hydrogen, and 2 R groups Tertiary- Carbon attached to the hydroxyl is attached to 3 R groups
What conditions are required for types of combustion?
Complete- A plentiful supply of oxygen Incomplete- A limited supply of oxygen
What are the conditions and reagents needed to produce an aldehyde from an alcohol?
Gently heat a primary alcohol with acidified potassium dichromate under distillation (to prevent further oxidation)
What substance works with alcohols to oxidise it and how is it chemically changed?
Dichromate(VI) is reduced to Chromium(III) Orange to Green Allows oxidation
How do you prepare a carboxylic acid from an alcohol?
Strongly heat a primary alcohol with an excess of acidified potassium dichromate under reflux, to allow of it to be oxidised
How do you prepare a ketone from an alcohol?
Heat a secondary alcohol with an excess of acidified potassium dichromate under reflux, so it fully oxidises
How do you oxidise tertiary alcohols?
Not possible
What type of reaction and conditions are needed for the dehydration of alcohols?
Heat under reflex with a concentrated acid catalyst, like H2SO4 Elimination, two products are possible
What are the steps of reacting an alcohol to produce a haloalkane?
Heat under reflux with H2SO4 and NaBr 1) Acid + NaBr forms NaHSO4 and HBR 2) HBr + Alcohol forms a haloalkane and Water Overall Acid + Alcohol + Salt forms Haloalke Water and NaHSo4
Why do you use distillation for the production of aldehydes?
Removes the aldehyde from the reaction mix before it can be oxidised further