Chemistry: Alcohols Part 2
This flashcard set highlights the three major reactions alcohols undergo: combustion, elimination, and oxidation. It explains that alcohols burn in oxygen to produce carbon dioxide and water, and notes that their combustion is more efficient than alkanes due to the presence of an oxygen atom in their structure.
what three important reactions do alcohols take part in
combustion
elimination
oxidation
Key Terms
what three important reactions do alcohols take part in
combustion
elimination
oxidation
what do alcohols burn in oxygen to form
co2 and water
why do alcohols combust more efficiently than alkanes
presence of O atom
what does an alcohol react to form in an elimination reaction
an alkene
elimination
a reaction in which an atom/group of atoms is removed from a reactant
why do elimination reactions of alcohol involve dehydration
water is eliminated
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| Term | Definition |
|---|---|
what three important reactions do alcohols take part in |
|
what do alcohols burn in oxygen to form | co2 and water |
why do alcohols combust more efficiently than alkanes | presence of O atom |
what does an alcohol react to form in an elimination reaction | an alkene |
elimination | a reaction in which an atom/group of atoms is removed from a reactant |
why do elimination reactions of alcohol involve dehydration | water is eliminated |
| conc h2so4 |
conditions elimination | heat |
elimination of alchools what happens |
|
what can alcohols be oxidised by | oxidising agents such as acidifed potassium dichromate |
what happens to acidified potassium dichromate when it acts as an oxidising agent | changes orange to green |
half equation oxidation of alcohols | Cr2O72- + 14H+ + 6e- > 2Cr3+ + 7h2o |
what is a primary alcohol oxidised to | an aldehyde and then to a carboxylic acid |
general equation oxidation of primary alcohol | RCH2OH + {O} > RCOH + H2O |
reagent and conditions oxidation primary | acidified potassium dichromate/ H+ gentle heat and distil |
observation oxidation primary | orange to green |
why is the product of oxidation of primary alcohol likely to be an aldehyde | aldehyde will have lower boiling point than alcohol it was formed from |
oxidation of ethanol symbol equation | CH3CH2OH + [O] > CH3CHO + H2O |
oxidation to carboxylic acid general equation | RCH2OH + 2[O] > RCOOH + H2O |
why is it 2[O] in symbol equation oxidation to carboxylic acid | alcohol being oxidised further |
conditions oxidation to carboxylic acid | cr2o72-/H+ heat and reflux |
why is product likely to be carboxylic acid |
- no products able to condense and separate |
how can the carboxylic acid be removed from the reaction mixture when the reaction is complete | distillation |
oxidation of ethanol to carboxylic acid symbol equation | CH3CH2OH + 2[O] > CH3COOH H2O |
what is a secondary alcohol oxidised to | a ketone |
can ketones be oxidised | no |
general equation oxidation secondary alcohols | RCOHR1 + [O] > RCOR1 + H2O |
reagents and conditions oxidation secondary alcohol | acidified potassium dichromate | heat and relflux |
symbol equation oxidation of propan-2-ol (seoncdary) | CH3CHOHCH3 + [O] > CH3COCH3 + H2O |
Apparatus for oxidation to a carboxylic acid | Reflux |
Apparatus oxidation of primary alcohols | Immediate distillation |
| Using mild oxidising agents such as tollens or fehlings |
Observations tollens reagent | Silver mirror seen |
Organic product silver mirror test | Carboxylic acid |
Observations fehlings solution | Blue solution to brick red pot |
How can the presence of a carboxylic acid functional group be confirmed | Using sodium carbonate |
Observations carboxylic acid and sodium carbonate | Effervescence |
Organic product sodium carbonate and carboxylic acid | Carboxylate salt RCOO-Na+ |
General equation carboxylic acid and sodium carbonate | 2RCOOH+ Na2CO3 > 2RCOONa + CO2 + H2O |