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]
www.tutorsglobe.com offers nucleophilic addition & reduction homework help, assignment help, online tutoring assistance, organic chemistry solutions by online qualified tutor's help.
tutorsglobe.com attitudes toward risktaking assignment help-homework help by online choice under uncertainty tutors
the third generation computers were come into existence in the year 1964. they employed integrated circuits (ics) in it.
tutorsglobe.com prevention of establishment of organism assignment help-homework help by online prophylaxis of diphtheria tutors
tutorsglobe.com medicinal plants including microbes assignment help-homework help by online crop diseases and their control tutors
tutorsglobe.com cataract assignment help-homework help by online optometry tutors
www.tutorsglobe.com offers Object Oriented Language homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
the computer based system has been introduced in the market, many years ago. it has made its powerful place in some decades of time.
www.tutorsglobe.com offers history homework help, history assignment help, online tutoring assistance, history solutions by online qualified and experienced history tutor's help.
If the business giving the goods or service were to wait until the contract is totally fulfilled before recognising revenue, the income statement could provide a misleading notion of the wealth produced in the several accounting periods covered through the contract.
tutorsglobe.com protein metabolism assignment help-homework help by online biochemistry tutors
There is a unique adjustment for every channel. Resonance is acquired with coil’s distributed capacitance, stray and trimmer capacitors. The oscillator coil is generally constructed with an aluminium or brass screw as the core for fine tuning.
Determination of the Percent Oxygen in Air tutorial all along with the key concepts of Theory of determination of the percent oxygen in air, Procedure of determination of the percent oxygen in air, Computations of determination of the percent oxygen in air
ionic or salt-like hydrides tutorial all along with the key concepts of covalent hydride, metallic hydrides, electronegativity values, formation of hydrides, white crystalline solids
TutorsGlobe.com Reabsorption in Henles loop Assignment Help-Homework Help by Online Mechanism of urine formation Tutors
1954544
Questions Asked
3689
Tutors
1455613
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!