Chemistry 4.3 - Alcohols

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Primary alcohols have...
One R group attached to the carbon bearing the -OH.
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Secondary alcohols have...
Two R groups attached to the carbon bearing the -OH.
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How do you distinguish between primary and secondary alcohols?
LUCAS TEST - zinc chloride in concentrated HCl. Secondary alcohols will show cloudiness.
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Name the four methods for producing an alcohol.
1. Nucleophilic sub of halogenoalkanes. 2. Reduction of aldehydes, ketones or carboxylic acids. 3. Fermentation (only applies to ethanol). 4 . Catalytic hydration of ethene.
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Conditions for the nucleophilic substitution of a halogenoalkane to produce an alcohol?
Halogenoalkane, aqueous NaOH and reflux.
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What is a nucleophile?
An electron donor.
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Heterolytic bond fission.
The uneven splitting of a bond in which one of the bonded atoms receives both of the bonded electrons.
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Conditions for the reduction of aldehydes and ketones.
Aqueous sodium borohydride.
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How do you represent the reducing agent in the equation?
2[H].
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Conditions for the reduction of c.acids?
Lithium aluminium hydride dissolved in ether. The ether makes the conditions anhydrous, as LiAlH4 reacts violently with water.
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Problems with using lithium aluminium hydride as a reducing agent?
1. Reacts violently with water. 2. Difficult to dispose of. 3. Ether is extremely flammable.
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Conditions for the fermentation of glucose?
Yeast, 30-40'C, anaerobic.
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Why should the conditions be kept anaerobic?
In aerobic conditions ethanol will oxidise to form ethanoic acid.
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Advantages of fermentation?
1. Uses renewable energy sources (plant material). 2. Reasonable temperature range. 3. Gentle atmospheric pressure.
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Disadvantages of fermentation?
1. Releases carbon dioxide, a greenhouse gas. 2. Very slow.
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Conditions for the catalytic hydration of ethene?
1. Phosphoric acid. 2. Silicon dioxide catalyst. 3. Water 4. 300'C 5. 60-70 atm.
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Advantages of catalytic hydration?
1. Rapid rate of reaction. 2. High yield.
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Disadvantages?
1. High temperatures and pressures = high energy input. 2. Costly industrial process. 3. Uses finite resources based on crude oil.
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State the 3 reactions of alcohols.
1. Hydrogen halides. 2. Acid (acyl) chlorides. 3. C.acids.
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Conditions for the chlorination of alcohols.
Hydrogen chloride gas, anhydrous zinc chloride.
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Conditions for the bromination of alcohols?
Potassium bromide, concentrated sulfuric acid catalyst.
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Bromination is an 'in-situ' reaction. Explain what this means.
An in-situ reaction is when chemical species are produced within the reaction mixture. In this case, the sulfuric acid protonates the alcohol (alcohol gains a proton), which then reacts with the bromine ions.
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Acyl group?
R-C(O)-
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Acyl chlorides are very reactive. Why?
Their carbon is extremely electron deficient. They are bonded to two very electronegative atoms: Cl and O.
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Name the mechanism by which the reaction between acyl chlorides and alcohols occurs.
Nucleophilic addition elimination.
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What is a zwitterion?
A molecule/ion that has separate positively and negatively charged groups.
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What is an oxoanion?
An anion derived from the loss of hydrogens bound to an oxygen.
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Why is this reaction important?
Increases the length of the carbon chain, increasing the number of further reactions.
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Conditions for esterification?
Concentrated sulfuric acid, reflux.
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When drawing the ester produced, which part comes first? The c.acid part of the alcohol part?
The c.acid part.
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Reflux.
Constant evaporation and decondensation of a liquid to ensure none is lost from the mixture.
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Reflux creates an...
Equilibrium mixture.
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Carboxylic acid vs acyl chlorides. Which reaction is better?
ACYL CHLORIDES produce a higher yield of ester as the reaction is not reversible and increase the length of the carbon chain for further reactions. HOWEVER, HCl fumes can be given off = toxic.
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How to test for halogenalkanes?
Addition of nitric acid to remove impurities, followed by silver nitrate.
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Chloride ions?
White ppt.
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Bromide ions?
Cream ppt.
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Iodide ions?
Yellow ppt.
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How would you distinguish between chloride and bromide ions?
Dissolve in dilute ammonia. The white ppt of Cl- will redissolve.
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How would you distinguish between bromide and iodide ions?
Dissolve in conc ammonia. The cream ppt of the Br- ions will redissolve.
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Card 2

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Secondary alcohols have...

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Two R groups attached to the carbon bearing the -OH.

Card 3

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How do you distinguish between primary and secondary alcohols?

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Preview of the front of card 3

Card 4

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Name the four methods for producing an alcohol.

Back

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Card 5

Front

Conditions for the nucleophilic substitution of a halogenoalkane to produce an alcohol?

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