1. fuel 2. cosmetics 3. drinks industry 4. antiseptics 5. perfumes

O- Alcohols Flashcards by Katherine Choi

State + explain the C-O-H bond angle in ethanol.

104
- repulsion betw. 2 lone pairs on O
- C-O & O-H bonds pushed closer tgt

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What types of IMF do you expect to find between molecules of pentan-1-ol?

H bonds
vdW (C-H bonds)

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Explain whether methanol and hexanol will dissolve in water.

ability to dissolve in water depends on ability to form H bonds w/ water
- methanol dissolves- ↑ polar ∵shorter hydrocarbon chain (OH takes up larger portion)
- hexanol x dissolve- longer non-polar alkyl chain

water = polar –> only dissolves polar

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What happens to solubility of alcohols as the length of carbon chain increases?

↓
- ↑ vdW
- ↓ H bonding character

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Uses of ethanol

fuel
cosmetics
drinks industry
antiseptics
perfumes

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What are the 2 methods of forming ethanol?

hydration of ethene
fermentation of glucose

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Name the process that crude oil must undergo before it is able to be used.

Fractional distillation

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Name the process used to form ethene after fractional distillation.

Cracking

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What is hydration?

adding water (across a double bond)

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Conditions for hydration of ethene.

conc H3PO4 (used in industry)- catalyst
steam
high pressure
300oC

conc H2SO4 can also be used but H3PO4 in industry

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What is the raw material for hydration of ethene?

crude oil

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State the overall equation for hydration of ethene.

C2H4 (g) + H2O (g) –> C2H5OH(l)

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Advantages for hydration of ethene.

faster synthesis
continual process
purer product

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Disadvantages for hydration of ethene.

non-renewable (crude oil)
↑ energy costs (↑temp etc.)

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What is the raw material for fermentation of glucose?

plants

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How is the raw material processed in fermentation of glucose?

amylolytic enzymes
break down starch –> glucose

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State the overall equation for fermentation of glucose.

C6H12O6 (aq) –> 2C2H5OH (aq) + 2CO2 (g)

Conditions for fermentation of glucose.

yeast
anaerobic (prevent ethanol being oxidised into ethanoic acid)
35oC- compromise (↓ temp = ↓ rate; ↑ temp = enzymes denature)

Does fermentation of glucose have a 100% atom economy?

x
- ethanol = desired product
- CO2 formed alongisde

When the reaction stop in fermentation of glucose + what happens next?

when solution contains 15% ethanol –> enzymes stop functioning
ethanol separated from miture by fractional distillation —to purify
∵ bp of water & ethanol are diff.

bp of ethanol ¬ 78oC

Advantages of fermentation of glucose.

renewable
↑ environmentally friendly
low tech
carbon neutral
milder conditions (↓ temp + pressure)

Disadvantages of fermentation of glucose.

non-continual process
↓ pure product

Give 2 examples of oxidation

combustion
rusting

What is oxidation?

gain of O2
loss of e-

What oxidises alcohols?

**oxidising agent:** *acidified* potassium dichromate *H+*/K2Cr2O7

How do you know an alcohol has been oxidised?

solution: orange --> green

Outline steps of primary alcohol oxidation.

**Repeat** oxidation: 1. alcohol '**OH**' --- H+/ K2Cr2O7---> aldehyde '**CHO**' 2. aldehyde ---H+/ K2Cr2O7---> carboxylic acid '**COOH**' eg. ethan**ol**-->ethan**al**-->ethan**oic acid**

What could be the problem of repeat oxidation?

when we only want to form one of the products (aldehyde/ carboxylic acid)--> ways to control reaction

How do we control oxidation of a primary alcohol?

- **aldehyde** (singular oxidation)**-** H+/ K2Cr2O7 + **distillation** - **carboxylic acid** (further)**-** H+/ K2Cr2O7 + **reflux**

Setup + keypoints for distillation

- **closed system w/ thermometer** - **heating mantle** (instead of bunsen burner)- ethanol is v. flammable - **anti-bumping granules**- ✔ even boiling, prevent large bubbles - **iced water** (conical flask containing distillate submerged in)- so aldehyde product x evaporate

What is reflux?

- mixture of liquids - heated to **bp** - for a **long time** | used when substance has low bp/ volatile

How does reflux work?

- **vapour** formed **escapes** from the reaction vessel - converted back into a liquid- **condenses** as it gets cooler further up the **Liebig condenser** - so any ethanol/ ethanal evaporated ✔ **oxidised**

Outline secondary alcohol oxidation.

- alcohol ---H+/ K2Cr2O7---> **ketone** 'one' (=O) - eg. CH3CH(OH)CH3 --> CH3C**(O)**CH3 only **singlar** oxidation ∵ repeat oxidation would involve breaking a **C-C bond**- **too strong**

Outline tertiary alcohol oxidation

**x be oxidised** * ∵ would involve breaking a **C-C** bond- **too strong**

What is lost from alcohol in alcohol elimination?

H2O- dehydration

What is the reagent for alcohol elimination?

**conc**. H2SO4

What are the conditiona for alcohol elimination?

1. 600K 2. Al2O3 catalyst

Outline what happens in alcohol elimination.

1. **lone pair** on O move to H+ 2. **C-O** bond breaks--> e- move to **e- deficient O** (+) 3. **C-H** bond breaks--> **C=C** forms 4. alkene

Is alcohol elimination selective in forming products?

- x selectivity - ∵ go via **carbocations**

Test for carboxylic acid

- react w/ **carbonate** - bubbles of **CO2**

Why is it hard to distinguish between aldehydes and ketones?

look + react v. similarly

Chemical tests to distinguish between aldehydes & ketones

separate mixtures of *aldehyde* & ketone 1. **Tollens reagent**- *silver mirror* formed vs x visible change// 2. **warmed in Fehlings reagent**- *blue --> brick-red* vs x visible change ## Footnote Fehling's is blue ∵ Cu2+ ions