alcohols Flashcards
What dangers are there with some alcohols?
Methanol, ethanol, and propanol are very flammable.
Why do alcohols have a low volatility and high b.p.?
As they can form hydrogen bonds which require more energy to overcome.
Why are shorter chain alcohols more soluble in water
The func:onal group, which forms hydrogen bonds with water molecules making it soluble, forms a greater proportion of the molecule
What are the reagents for the oxidaJon of primary and secondary alcohols and where are they from?
● An excess of… ○ Cr2O72-.
○ H+.
● From solu:on of potassium dichromate (VI) and dilute sulfuric
acid.
Something such as hydrochloric acid cannot be used as the dichromate ions would rather oxidise this.
What is the equaJon for the parJal oxidaJon of primary alcohols
A primary alcohol reacts with [O] (the oxidising agent) to form an aldehyde and water.
What are the reacJon condiJons for the parJal oxidaJon of primary alcohols and why
Dis:lling the aldehyde as it forms otherwise it will con:nue onto form a carboxylic acid
What is observed (colour- wise) under the oxidation of alcohols
Orange to green colour change.
Describe the setup for disJllaJon with an explanaJon for the key points
Bulb of thermometer at T-junc:on - to display the correct b.p.
● Water entering via bogom of condenser - en:re condenser
will fill up before water exits.
● Electric heater - prevents highly flammable organic
compounds se_ng alight under a live flame.
What is the equaJon for the full oxidaJon of a primary alcohol? Explain it
Primary alcohol + 2[O] → carboxylic acid + water
1. Two lots of oxidising agent is required; one for each stage
2. The water was produced at the first stage (when forming
aldehyde)
You can disBll aTerwards to remove any unreacted alcohol molecules.
What are the reacJon conditions for the full oxidation of primary alcohols and oxidation of secondary alcohols and why
Hea:ng under reflux to prevent evaporation
Describe reflux setup
● Open end - prevents build up of gas that can cause explosion
● An:-bumping granules - prevents vigorous and uneven boiling
by forming smaller bubbles
When is the reflux setup most ogen used?
When hea:ng organic reac:on mixtures for long periods.
What is the equaJon for oxidaJon of secondary alcohols?
Secondary alcohol + [O] → ketone + water
Why won’t terJary alcohols oxidise?
As you need to remove a 1H atom from the carbon the -OH is bonded to (alongside the 1H from the -OH subs:tuent group). Yet, no 1H is bonded to said carbon.
What are the products and conditions for the dehydration of alcohols and why
Forms an alkene and water.
● HEAT under reflux.
● Concentrated sulphuric or phosphoric acid.
● As we don’t want any water to form alcohols again.
