Alcohols Flashcards

Alcohols

A-Level AQA Chemistry

This pack of flashcards provides comprehensive coverage on the chemistry of alcohols, including their naming conventions, properties, and reactions such as oxidation and dehydration. It also addresses alcohol-related procedures like distillation and reflux, the role of catalysts and reagents, and the production of ethanol via fermentation, highlighting the concept of biofuels and carbon neutrality.

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How does the acid catalyst play a role in the reaction of alcohols with dehydrating agents?	The acid catalyst facilitates the removal of a water molecule from the alcohol molecule, promoting the formation of the alkene.
What are the advantages of fermentation over industrial formation from ethene?	Faster reaction, purer product, continuous process, and the use of a renewable resource (sugar).
What are the essential conditions for fermentation?	Temperatures of 30-40°C, no air, and the presence of yeast.
Define hydration.	Hydration is the addition of water to a molecule.
What is the reagent used in the fermentation process?	Yeast.
Describe the two methods for producing ethanol.	Fermentation and industrial formation from ethene.
Explain the acid-catalyzed elimination mechanism in the reaction of alcohols with dehydrating agents.	The acid catalyst, such as concentrated sulfuric or phosphoric acid, donates a proton (H+) to the alcohol molecule, leading to the formation of a carbocation. The carbocation then undergoes a rearrangement or elimination of a water molecule to form the alkene product.
What is the possible route to polymers without using monomers derived from oil?	Producing alkenes from alcohols provides a possible route to polymers without using monomers derived from oil.
Describe the type of reaction that occurs during the dehydration of alcohols.	The reaction is an acid-catalyzed elimination reaction, where a water molecule is eliminated from the alcohol molecule to form an alkene.
What are the disadvantages of industrial formation from ethene?	High technology equipment needed, ethene is a non-renewable resource, batch process, high energy costs, and the ethanol produced is not pure.
Define a dehydrating agent.	A dehydrating agent is a substance that removes water from a compound.
What are the reagents used in the dehydration reaction of alcohols?	The reagents used are concentrated sulfuric or phosphoric acids.
Describe the reaction of alcohols with dehydrating agents.	The reaction involves the of alcohols intokenes by removing a water molecule from the alcohol molecule.
How can the presence of a carboxylic acid be tested?	The presence of a carboxylic acid can be tested by adding sodium carbonate, which will produce fizzing and carbon dioxide.
What is the observation when aldehydes react with Fehling's solution?	When aldehydes react with Fehling's solution, the blue Cu2+ ions in the solution change to a red precipitate of Cu2O.
What is the observation when aldehydes react with Tollens' reagent?	When aldehydes react with Tollens' reagent, a silver mirror forms coating the inside of the test tube.
Define tertiary alcohols.	Tertiary alcohols are alcohols in which the carbon atom with the -OH group is bonded to three other carbon atoms. They cannot be oxidized by potassium dichromate due to the absence of a hydrogen atom bonded to the carbon with the -OH group.
How can Fehling's solution be used to distinguish aldehydes from ketones?	Fehling's solution is used to distinguish aldehydes from ketones. Aldehydes are oxidized by Fehling's solution, resulting in the reduction of copper (II) ions to copper(I) oxide.
What is the main disadvantage of fermentation?	It depletes land used for growing food crops.
What factors are not taken into account when determining if ethanol produced from fermentation is carbon neutral?	The energy needed to irrigate plants, fractionally distil the ethanol, and process the fuel, especially if the energy comes from fossil fuels.
Explain the overall net contribution of CO2 to the atmosphere in the production of ethanol from fermentation.	For every 6 molecules of CO2 absorbed, 6 molecules of CO2 are emitted, resulting in no net contribution of CO2 to the atmosphere.
How is ethanol produced from fermentation classified?	As a biofuel.
Define carbon neutral.	An activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere.
Describe what a biofuel is.	A fuel produced from plants.
What is the main disadvantage of industrial formation from ethene?	It uses a non-renewable resource (ethene) that will become more expensive when raw materials run out.
What is Tollens' reagent used for?	Tollens' reagent is used to distinguish aldehydes from ketones. Aldehydes are oxidized by Tollens' reagent to form a carboxylic acid, while ketones do not react.
What is the product of the acid catalysed addition mechanism for hydration of ethene?	Ethanol.
What is the role of conc H3PO4 in the acid catalysed addition mechanism for hydration of ethene?	It provides the H+ ions necessary for the reaction.
What is the role of yeast in fermentation?	Yeast acts as a catalyst to convert glucose into ethanol and carbon dioxide.
What happens to the ethanol produced in fermentation when air is present?	It oxidizes to ethanoic acid (vinegar).
What is the type of reaction involved in fermentation?	Fermentation is a hydration/addition reaction.
Why is fermentation done in the absence of air?	The presence of air can cause extra reactions to occur.
What is the optimum temperature for fermentation?	Around 38°C.
What is the purpose of using a strong acidic catalyst in the acid catalysed addition mechanism for hydration of ethene?	To provide H+ ions for the reaction.
Describe the partial oxidation of primary alcohols.	The reaction involves the conversion of a primary alcohol to an aldehyde. The aldehyde has a C=O bond on the first carbon of the chain.
How can the yield of distillate be maximized during distillation?	To maximize the yield of distillate, only collect it at the approximate boiling point of the desired aldehyde and not higher.
What is the role of sulfuric acid in the oxidation of alcohols?	Sulfuric acid is used as a reagent in the oxidation of alcohols.
Define aldehyde.	An aldehyde is a type of organic compound that always has a C=O bond on the first carbon of the chain and ends in -al in its name.
What is the purpose of cooling the collection flask in ice during distillation?	Cooling the collection flask in ice helps improve the yield of distillate.
Why are electric heaters often used to heat organic chemicals in dist?	Electric heaters are used because organic chemicals are highly flammable and could set on fire with a naked flame.
How should the apparatus for distillation be drawn and labeled?	The apparatus should include a round-bottomed flask, a thermometer, an adaptor, a Liebig condenser. The bulb of the thermometer should be at the T junction connecting to condenser.
What is the purpose of distillation in organic chemistry?	Distillation is used as a separation technique to separate an organic product from its reacting mixture.
What is the purpose of adding a limited amount of dichromate in the oxidation of primary alcohols?	Adding a limited amount of dichromate helps control the reaction and prevents over-oxidation of the primary alcohol.
What is the role of potassium dichromate in the oxidation of alcohols?	Potassium dichromate is an oxidizing agent that causes alcohols to oxidize.
Describe the solubility of smaller alcohols in water.	Smaller alcohols can dissolve in water because they can form hydrogen bonds with water molecules.
What is the prefix used to name alcohols with two or more -OH groups?	Di, tri, etc. are used as prefixes.
Define primary alcohols.	Primary alcohols are alcohols where 1 carbon is attached to the carbon adjoining the oxygen.
What is the reason for the relatively high boiling points of alcohols?	Alcohols have the ability to form hydrogen bonds between alcohol molecules.
Describe the bond angles in alcohols.	All the H-C-H bonds and C-O are 109.5° (tetrahedral shape), while the H-O-C bond is 104.5° (bent line shape) due to repulsion from lone pairs of electrons.
How are alcohols named?	They have the ending -ol and if necessary, the position number for the OH group is added between the name stem and the -ol.
What are the reagents used for the full oxidation of primary alcohols?	The reagents used are potassium dichromate(VI) solution and dilute sulfuric acid.
What is the difference between aldehydes and ketones in terms of further oxidation?	Aldehydes can be further oxidized to carboxylic acids, while ketones cannot be further oxidized.
Describe the oxidation of secondary alcohols.	Secondary alcohols are oxidized to ketones using potassium dichromate(VI) solution and dilute sulfuric acid under heat and reflux conditions.
What precautions should be taken when using a condenser in reflux?	The condenser should not be sealed at the end to prevent gas pressure build-up, and it should have two openings for water in and out.
Describe the round-bottomed flask used in reflux.	The round-bottomed flask is an important component of the apparatus and should be accurately drawn and labeled.
What are anti-bumping granules used for in reflux and distillation?	Anti-bumping granules prevent vigorous and uneven boiling by promoting the formation of small bubbles.
What is the purpose of reflux in the full oxidation of primary alcohols?	Reflux is used to heat the reaction mixture for long periods while preventing the escape of organic vapors.
What is the observation made during the full oxidation of primary alcohols?	The orange dichromate ion (Cr2O7-) reduces to the green Cr3+ ion.
Describe the conditions required for the full oxidation of primary alcohols.	The reaction requires an excess of dichromate and heating under reflux.
What is the general formula for alcohols?	CnH2n+1OH
What is the reaction that occurs during the full oxidation of primary alcohols?	The reaction is the conversion of a primary alcohol to a carboxylic acid.
What is the purpose of the thermometer in distillation?	The thermometer is used to measure the correct boiling point of the desired aldehyde during distillation.
Describe the oxidation equations of alcohols using [O] as a simplified form.	The oxidation equations involve the alcohol reacting with [O] from the oxidizing agent to form an aldehyde or a carboxylic acid, depending on the type of alcohol.
How should the formulae of aldehydes be written in a condensed way?	The formulae of aldehydes should be written as CHO and not COH, e.g., CH3CH2CHO.
What is the role of water in the condenser during distillation?	Water in the condenser provides efficient cooling and prevents backflow out of the condenser.

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