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]
want perfect philosophy of the emotions assignment help at the most rational price? get instant help from phd tutors!
theory and lecture notes of finite state machines all along with the key concepts of finite state machines, fsm examples, fsm applications and finite state controller. tutorsglobe offers homework help, assignment help and tutor’s assistance on finite state machines.
tutorsglobe.com law of dominance assignment help-homework help by online laws of mendel tutors
rigid body dynamics i tutorial all along with the key concepts of Translational Motion of a Rigid Body, Rotational Motion of Rigid Body, General Motion, Moment of Inertia, Radius of Gyration, Dumbbell, Moments and Couples
Statement of comprehensive income expands the conventional income statement to involve specific other gains and losses that influence the equity of shareholders.
What are Material Losses, The material losses are Waste, Scrap, Spoilage and Defectives. One of the major reasons of increasing material costs is the loss of material within the production process. It is of paramount significance
Fungi morphology tutorial all along with the key concepts of Unicellular Forms, Yeast, Slime Moulds, Cellular type, Plasmodial type, Filamentous Forms and Pseudoparenchymatous Forms
Theory and lecture notes of Costs of Inflation all along with the key concepts of Costs of Moderate Expected Inflation, Costs of Moderate Unexpected Inflation, Hyperinflation and Its Costs, Inflation Tax. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Costs of Inflation.
It is a unique kind of superhet receiver that receives code words. For that aim, it consists of Beat Frequency Oscillator.
elements of hydrodynamics tutorial all along with the key concepts of concept of streamlines and velocity, bernoulli's principle definition, applications of bernoulli's principle, change in kinetic energy of fluid, change in potential energy of the fluid
The concepts of financial accounting - Separate Entity, Double Entry, Money Measurement Concept, Going Concern Concept, Matching Concept.
conduction of heat tutorial all along with the key concepts of Conduction of Heat Energy, Factors Affecting Conduction, Thermal Conductivity of a Material, Lagged and Unlagged Bars, Measuring the Thermal Conductivity of a Good Conductor
IAS 7 defines cash like notes and coins in hand and deposits in banks and identical institutions which are accessible to the business on demand.
Having set out the major principles included in preparing an income statement, we required to consider some additional points.
Theory and lecture notes of Client-Server DBMS Architectures all along with the key concepts of Centralized DBMS, Physical Centralized Architecture, two-tier client server architecture. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Client-Server DBMS Architectures.
1943040
Questions Asked
3689
Tutors
1470956
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!