Introduction:
Aldehydes and ketones can be made as using different methods ranging from the oxidation to reduction of appropriate compounds.
Preparation of Aldehydes and ketones:
Aldehydes and ketones can be made by using the different methods illustrated below:
Oxidation of primary and secondary alcohols:
Aldehydes and ketones are made by the oxidation of primary and secondary alcohols correspondingly by using a mild oxidizing agent like acidified solution of potassium heptadicromate (VI) or tetraoxomanganate (VII).
Fig: Oxidation of primary and secondary alcohols
If potassium heptaoxodichromate (VI) acidified by dilute tetraoxosulphate (VI) acid is employed, a change in the colour of the solution from orange solution having the dichromate (VI) ions is reduced to the green solution having chromium (III) ions. The total effects is that an oxygen from the oxidizing agent eliminates one hydrogen atom from the -OH group of the alcohol and the other one from the carbon to which it is linked to form water.
Though in the oxidation of primary alcohols to form aldehydes, there is a problem. The aldehydes generated can be oxidized further to a carboxylic acid via the acidified dichromate (VI) solution employed as the oxidizing agent. This though can be prevented by employing surplus alcohol and limited oxidizing agent. As well by eliminating the aldehydes as soon as it is formed, this can be controlled.
Oxidative cleavage of alkanes (ozonolysis):
Ozone, if bubbled via a solution of an alkene in 1, 1, 1-trichloromethane, followed through the hydrolysis of the ozonide formed, in the presence of zinc and ethanoic acid provides aldehydes and ketones. The starting alkene finds out the product, if aldehydes or ketones.
Fig: Oxidative cleavage of alkanes
Dehydration of alcohols:
The lower members of aldehydes and ketones are made industrially by passing the alcohol vapor over hot copper catalyst.
Fig: Dehydration of alcohols
A primary alcohol provides aldehyde whereas a secondary alcohol provides ketone.
Decarboxylaton of calcium salts:
Aldehydes are prepared by heating a mixture of calcium methanoate and calcium carboxylate at 400oC. If calcium methanoate is not utilized, then a ketone is formed.
Fig: Decarboxylaton of calcium salts
Reduction of acyl chloride using a 'poisoned catalyst':
This reaction is termed as Rosenmund Reaction. This is only suitable for aldehydes. Acyl chlorides are reduced to aldehydes by treatment with hydrogen in the presence of Palladised barium tetraoxosulphate (VI), poisoned through barium tetraoxosulphate (VI). The catalyst is poisoned to prevent further reduction to the alcohol.
RCOCl + H2 + (Pd/BaSO4)/heat → RCHO + HCl
Friedel-Craft acylation:
The condensation of benzene by an acyl chloride, RCOCl, or acid anhydride, (RCO)2O, in the presence of anhydrous aluminum chloride-a Lewis acid provides a good yield of the aromatic ketone. The reaction mixture is refluxed on the water bath at around 50oC
RCOCl + AlCl3 → (at 50oC) → RC+O + [AlCl4]-
Or if the acid anhydride is employed,
Fig: Friedel-Craft acylation
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with a tutor at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online Chemistry tutoring. Chat with us or submit request at [email protected]
Theory and lecture notes of Graphs of Rational Functions all along with the key concepts of graphs of rational functions, homework help, assignment help, polynomials and rational functions tutors. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Graphs of Rational Functions.
tutorsglobe.com laboratory diagnosis and control assignment help-homework help by online clostridium botulinum tutors
tutorsglobe.com vernalization assignment help-homework help by online plant physiology tutors
We provide the best Cost Accounting Assignment Help from subject matter tutors to score top grades at viable prices.
tutorsglobe.com actinide series assignment help-homework help by online f block elements tutors
are assignments and coursework your biggest nightmare? avail aerospace engineering assignment help to secure maximum marks.
tutorsglobe.com neo-lamarckism assignment help-homework help by online lamarckism tutors
cell types tutorial all along with the key concepts of the plant cell wall, middle lamella, primary wall, secondary wall, kinds of plant cells, meristematic cells, sclerenchyma cells, kinds of animal cells, muscle cells and blood cells
Theory and lecture notes of Context sensitive grammars and languages all along with the key concepts of context sensitive grammars and languages, Context Free Grammars & Languages. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Context sensitive grammars and languages.
Metabolisms and Behavior in the Environment tutorial all along with the key concepts of Metabolism of Insecticides, Botanicals, Chlorinated Hydrocarbons, Organophosphorus Compounds, Methyl-Dimethyl Carbamates, Behavior-Properties of Pesticides, Fate of Pesticide in the Atmosphere
tutorsglobe.com factoring assignment help-homework help by online working capital management tutors
Work and Energy tutorial all along with the key concepts of Work Done by a Constant Force, Unit of Work, Work Done by Varying Force, Power, Kinetic Energy, Conservation of Energy
Environmental Management Systems Assignment Help work with the priority to ensure that all your queries bne answered on time.
Theory and lecture notes of Distributed transaction management all along with the key concepts of distributed transaction management, transaction management. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Distributed transaction management.
www.tutorsglobe.com offers Object oriented analysis Process homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
1952030
Questions Asked
3689
Tutors
1463344
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!