• Like

Loading…

Flash Player 9 (or above) is needed to view presentations.
We have detected that you do not have it on your computer. To install it, go here.

Reactions of alcohol

  • 24,864 views
Published

 

Published in Education , Technology , Business
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads

Views

Total Views
24,864
On SlideShare
0
From Embeds
0
Number of Embeds
1

Actions

Shares
Downloads
134
Comments
0
Likes
1

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Reactions of Alcohol
  • 2. Reactions of Alcohols
  • 3. Reactions of alcohols
    • Alcohols contain an –OH group covalently bonded to a carbon atom.
    • However, this –OH group does not behave in the same way as the hydroxide ion OH – because NaOH is a base and CH3OH is not.
    • Alcohols, when dissolved in water, do not alter the pH of the water.
    • Although the hydrogen atom is connected to an oxygen atom, alcohols do not readily donate the proton (they are weaker acids than water).
  • 4. Reactions of Alcohol
    • Like the alkanes and alkenes, alcohols undergo complete combustion in a plentiful supply of oxygen gas, producing only carbon dioxide and water as products.
    • You may have used alcohol burners in an investigation in chapter 6.
    • The complete combustion of ethanol is as follows:
  • 5.
    • When balancing an equation for the combustion of an alcohol it is important to remember that there is an oxygen atom in the alcohol, unlike alkanes and alkenes
  • 6. Oxidation of ethanol
    • The process of oxidation was defined in chapter 10 as the loss of electrons.
    • In organic chemistry oxidation is easily recognized as the gain of oxygen or the loss of hydrogen from a compound.
    • The oxidation reactions of alcohols vary, depending upon the type of alcohol involved.
    • Primary, secondary and tertiary alcohols all give different reactions with strong oxidizing agents such as acidified potassium dichromate(VI) solution or acidified potassium manganate(VII) solution.
  • 7.  
  • 8. Alcohol oxidizes to carboxylic acid
    • In the laboratory, when an aqueous solution of a primary alcohol such as ethanol is mixed with potassium dichromate (VI) and sulfuric acid, and the mixture heated under reflux, the alcohol is fully oxidized to a carboxylic acid.
  • 9.
    • During the process, the alcohol is initially oxidized to an aldehyde; however, by heating under reflux the aldehyde is further oxidized to a carboxylic acid.
    • When the reaction is ‘complete’, the condenser is turned around and the reaction mixture is distilled to collect an aqueous solution of the carboxylic acid.
    • If the aldehyde is the desired product during this reaction, then the reaction can be carried out at room temperature and the aldehyde can be distilled off from the mixture.
    • Some distillation apparatus is shown at the beginning of this chapter (p. 341).
  • 10.  
  • 11.
    • The oxidation reaction of the primary alcohol (e.g. ethanol) to a carboxylic acid may be represented simply by an equation in which the symbol [O] represents the oxygen supplied by the oxidizing agent:
  • 12. Alternatively, we may write half-equations and a complete equation to represent the redox nature of the reaction:
  • 13.
    • A secondary alcohol has the hydroxyl group on a carbon that is bonded to two other carbons. Propan-2-ol and butan-2-ol are examples of secondary alcohols.
  • 14. Secondary alcohol oxidation
    • When secondary alcohols are oxidized, ketones are formed.
    • This reaction is very similar to the one in which aldehydes are produced, but the placement of the hydroxyl group results in the production of a ketone rather than an aldehyde and, ultimately, a carboxylic acid.
  • 15.
    • The oxidation reaction of a secondary alcohol such as propan-2-ol to a ketone may be represented simply as:
  • 16.
    • Alternatively, we may write half-equations and a complete equation to represent the redox nature of the reaction:
  • 17.
    • When these oxidation reactions are performed in a laboratory investigation, the change in colour of the oxidizing agent indicates that the reaction has proceeded.
    • Potassium dichromate, K 2 Cr 2 O 7 , changes colour from orange (Cr 2 O 72– ) to green (Cr 3+ ) during this reaction. If potassium manganate(VII), KMnO 4 , is used instead, it changes colour from purple to colourless.
  • 18.
    • Tertiary alcohols, those with the hydroxyl group bonded to a carbon atom that is bonded to three other carbon atoms, are not easily oxidized.
    • An example of a tertiary alcohol is 2-methylpropan-2-ol.
  • 19.  
  • 20.