Alcohols and Mass Spec

Question 1

How is ethanol formed from sugars

Answer 1

Yeast, 25 to 42 degrees
Sugar is renewable
Equipment is cheap and low tech
Batch process = high production cost 
Very impure and required further processing
Slow process with low yield

Question 2

How is ethanol formed from hydration of ethene

Answer 2

Ethene is non renewable
Process is continuous therefore low production costs 
Uses a high temp, pressure and catalyst 
Expensive equipment 
Very fast, high yield and pure product

Question 3

How is ethanol used as a biofuel

Answer 3

Sugars from sugar cane are fermented to produce alcohol
This is added to petrol as a biofuel
It is carbon neutral

Question 4

What halogens in the oxidation of alcohols and what are the conditions

Answer 4

Oxidising agent: potassium dichromate (VI) - represented as [O]
Turns from orange to green

Primary alcohol - aldehyde - carboxylic acid
Distilled to get aldehyde, reflux to get carboxylic acid

Secondary alcohol - ketone

Tertiary alcohols cannot be oxidised as carbon with OH has no hydrogen to lose

Question 5

What is fehlings reduced to n the oxidation of alcohols

Answer 5

From deep blue to brick red when a ketone is present - precipitate formed

Question 6

What is Benedict’s reduced to in the oxidation of alcohols

Answer 6

Turns blue with a ketone

Question 7

What colour does Tollens go in the oxidation of alcohols

Answer 7

Turns from colourless to a silver mirror with an aldehyde

Question 8

What are the conditions needed for the dehydration of alcohols

Answer 8

Conc sulphuric acid at 180 degrees

Question 9

Why are high resolution mass specs used

Answer 9

Much more sensitive and accurate

Mr given to 4 dp which means different peaks, easier to identify compounds

Question 10

How does infrared spectroscopy work

Answer 10

Every bond stretches and moves at a specific frequency
Infrared makes the bonds vibrate, causing the bonds to absorb the infrared
Peaks below 1500 not important

Question 11

How are exact compounds identified in an infrared spectroscopy

Answer 11

Every compound has a distinct fingerprint region between 1500 and 400
An infrared spec is run on a known compound and compared to the spec of the unknown compound

Question 12

What are alcohols

Answer 12

General formula CnH2n+1

Classified as primary, secondary or tertiary