PMT 3.5 - Alcohols Flashcards

What is the functional group of an alcohol?

What is the functional group of an alcohol?

Hydroxyl group -OH

What is the general formula of an alcohol?

What is the general formula of an alcohol?

CnH2n+1OH

How do you name alcohols (one prefix, one suffix)?

How do you name alcohols (one prefix, one suffix)?

Hydroxyl- or -OH

What kind of intermolecular forces do alcohols have? Why?

What kind of intermolecular forces do alcohols have? Why?

Hydrogen bonding, due to the electronegativity difference in the OH bond

How do alcohols' m.p. And b.p. Compare to other hydrocarbons' of similar C chain lengths? Why?

How do alcohols' m.p. And b.p. Compare to other hydrocarbons' of similar C chain lengths? Why?

Higher, because they have hydrogen bonding → stronger than Van der Waals forces

Are alcohols soluble in water? Why does solubility depend on chain length?

Are alcohols soluble in water? Why does solubility depend on chain length?

Soluble when short chain - OH hydrogen, bonds to hydrogen bond in water

Insoluble when long chain - non-polarity of C-H bond takes precedence

What makes an alcohol primary?

What makes an alcohol primary?

C bonded to OH is only bonded to one other C atom

What makes an alcohol secondary?

What makes an alcohol secondary?

C bonded to OH is bonded to two other C atoms

What makes an alcohol tertiary?

What makes an alcohol tertiary?

C bonded to OH is bonded to three other C atoms

How can ethanol be made from crude oil?

How can ethanol be made from crude oil?

Hydration of ethene via electrophilic addition (phosphoric acid catalyst H₃PO₄)

What are the advantages and disadvantages of hydration of ethanol?

What are the advantages and disadvantages of this method?

Advantages - fast, continuous process, ethanol has a high purity

Disadvantages - not renewable as from crude oil

How can ethanol be made by fermentation?

How can ethanol be made by fermentation?

yeast enzymes break down sugars like glucose into ethanol and carbon dioxide in an anaerobic environment

What conditions are needed for this reaction to take place?

What conditions are needed for this reaction to take place?

Enzymes in yeast as catalyst, 35°C, anaerobic conditions

Write an equation for the reaction which takes place.

Write an equation for the reaction which takes place.

C6H12O6 (aq) → 2C2H5OH + 2CO2

What are the advantages and disadvantages for the fermentation method?

What are the advantages and disadvantages of this method?

Advantages - renewable as from plants

Disadvantages - slow, batch process, enzymes stop working at 15% alcohol so solution is not pure, needed to be fractionally distilled

In the future, how might most ethene be made? Why is it not made like this at the moment?

In the future, how might most ethene be made? Why is it not made like this at the moment?

Dehydrate ethanol made by fermentation → ethene

Not economical at the moment

Define carbon neutral

Define carbon neutral

an activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere 

Explain how using ethanol in petrol engines could be considered to be carbon neutral.

Explain how using ethanol in petrol engines could be considered to be carbon neutral.

Carbon dioxide released in fermentation and combustion = carbon dioxide absorbed when growing

Why would it not be entirely carbon neutral to use ethanol?

Why would it probably not be entirely carbon neutral to use ethanol?

Other "carbon costs" associated with it e.g. Transport

What is a commercial fuel that uses ethanol? What else does it contain and why?

What is a commercial fuel that uses ethanol? What else does it contain and why?

Methylated spirits - methanol (toxic, so it can't be drunk)

Write an equation for the combustion of ethanol.

Write an equation for the combustion of ethanol.

C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2O (l)

What is an elimination reaction?

What is an elimination reaction?

The removal of a smaller molecule from a larger one

Which group leaves the parent molecule in the case of alcohols?

Which group leaves the parent molecule in the case of alcohols?

OH and a H (to form water)

What physical conditions are needed for the elimination reaction from alcohols to alkenes?

What physical conditions are needed for the elimination reaction from alcohols to alkenes?

Excess hot concentrated sulphuric acid

Draw a mechanism for the dehydration of ethanol.

Draw a mechanism for the dehydration of ethanol.

Draw a method for dehydration of ethanol in the lab.

Draw a method for dehydration of ethanol in the lab.

What forms if you partially oxidise a primary alcohol?

What forms if you partially oxidise a primary alcohol?

An aldehyde

What conditions are needed to partially oxidise a primary alcohol?

What conditions are needed to partially oxidise a primary alcohol?

Dilute sulphuric acid, potassium dichromate (VI), distill product as it's produced, gentle heating

Write an equation for the partial oxidation of ethanol

Write an equation for the partial oxidation of ethanol

CH3CH2OH (l) + [O] → CH3CHO (g) + H2O (l)

What forms if you fully oxidise a primary alcohol?

What forms if you fully oxidise a primary alcohol?

A carboxylic acid

What conditions are needed for full oxidation?

What conditions are needed for this reaction?

Concentrated sulphuric acid, potassium dichromate (VI), heating under reflux

Write an equation for the full oxidation of ethanol

Write an equation for the full oxidation of ethanol

CH3CH2OH (l) + 2[O] → CH3COOH (g) + H2O (l)

What forms if you oxidise a secondary alcohol?

What forms if you oxidise a secondary alcohol?

A ketone

Why can it not be oxidised further and why can't a tertiary alcohol be oxidised?

Why can it not be oxidised further and why can't a tertiary alcohol be oxidised?

A carbon-carbon bond would have to break

What conditions are needed for the oxidation of a secondary alcohol?

What conditions are needed for the oxidation of a secondary alcohol?

Concentrated sulphuric acid, potassium dichromate (VI), heating under reflux

Write an equation for the oxidation of propan-2-ol.

Write an equation for the oxidation of propan-2-ol.

CH3CH(OH)CH3 (l) + [O] → CH3COCH3 (g) + H2O (l)

What is an aldehyde? What is its functional group?

What is an aldehyde? What is its functional group?

Molecule with C=O group at the end of a carbon chain, carbonyl functional group (C=O)

How do you name aldehydes? Give an example.

How do you name aldehydes? Give an example.

Suffix -al

e.g. ethanal

What is a ketone? What is its functional group?

What is a ketone? What is its functional group?

Molecule with C=O group in the middle of a carbon chain, carbonyl functional group (C=O)

How do you name ketones? Give an example?

How do you name ketones? Give an example?

Suffix -one

e.g. propanone

What is a carboxylic acid? What is its functional group?

What is a carboxylic acid? What is its functional group?

Molecule with a COOH group, which has to be at the end of a carbon chain.

Carboxyl functional group (made up of carbonyl C=O and hydroxyl -OH group)

How do you name carboxylic acids? Give an example

How do you name carboxylic acids? Give an example

Suffix -oic acid

e.g. propanoic acid

What does the Tollens' test give a positive result for?

What does the Tollens' test give a positive result for?

aldehydes

What is in Tollens' reagent? How does this react with the substance to be tested?

What is in Tollens' reagent? How does this react with the substance to be tested?

Silver nitrate in NH3 (aq) - oxidises aldehydes but not ketones

Complex silver (I) ions reduced to Ag(s)

How do you carry out the Tollens' test?

How do you carry out the Tollens' test?

Add equal volumes of substance being tested and tollen's reagent to a test tube, leave in water bath for 10mins and observe any changes

What is the result of the Tollen's test for aldehydes and ketones?

What is the result of the Tollen's test for aldehydes and ketones?

Aldehydes - silver mirror forms (solid Ag)

Ketones - no visible change

What does Fehling's solution give a positive test result for?

What does Fehling's solution give a positive test result for?

aldehydes

What is in Fehling's? How does this react with the substance to be tested?

What is in Fehling's? How does this react with the substance to be tested?

Blue copper (II) complex ions - gentle oxidising agent

Reduced to Cu+ ions (brick red)

What conditions do you need to use the Fehling's solution?

What conditions do you need to use the Fehling's solution?

Heat

What result do aldehydes and ketones give in the fehlings test?

What result do aldehydes and ketones give in the fehlings test?

Aldehydes- brick red ppt

Ketones- no visible change