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Using Tollens' Reagent (The Silver Mirror Test):
Tollens' reagent contains the diamminesilver(I) ion, [Ag(NH3)2]+.
This is made from silver(I) nitrate solution. You add a drop of sodium hydroxide solution to give a precipitate of silver(I) oxide, and then add just enough dilute ammonia solution to redissolve the precipitate.
To carry out the test, you add a few drops of the aldehyde or ketone to the freshly prepared reagent, and warm gently in a hot water bath for a few minutes.
- Ketone : No change in the colourless solution.
- Aldehyde : The colourless solution produces a grey precipitate silver, or a silver mirror on the test tube.
Aldehydes reduce the diamminesilver(I) ion to metallic silver. Because the solution is alkaline, the aldehyde itself is oxidised to a salt of the corresponding carboxylic acid.
- 2Ag(NH3)2+ + RCHO + 3OH- ____} 2Ag + RCOO- + 4NH3 + 2H2O
Using Fehling's Solution or Benedict's Solution:
Fehling's solution and Benedict's solution are variants of essentially the same thing. Both contain complexed copper(II) ions in an alkaline solution.
Fehling's solution contains copper(II) ions complexed with tartrate ions in sodium hydroxide solution. Complexing the copper(II) ions with tartrate ions prevents precipitation of copper(II) hydroxide.
Benedict's solution contains copper(II) ions complexed with citrate ions in sodium carbonate solution. Again, complexing the copper(II) ions prevents the formation of a precipitate - this time of copper(II) carbonate.
Both solutions are used in the same way. A few drops of the aldehyde or ketone are added to the reagent, and the mixture is warmed gently in a hot water bath for a few minute
- Ketone: No change in the blue solution
- Aldehyde: The blue solution produces a dark red precipitate of copper(I) oxide.
- RCHO + NaOH +Cu(OH)2 ____} RCOONa + Cu2O + 3H2O
Using Acidified Potassium Dichromate(VI) Solution:
A small amount of potassium dichromate(VI) solution is acidified with dilute sulphuric acid and a few drops of the aldehyde or ketone are added. If nothing happens in the cold, the mixture is warmed gently for a couple of minutes - for example, in a beaker of hot water. Kketone No change in the orange solution. Aldehyde Orange solution turns green.
The orange dichromate(VI) ions have been reduced to green chromium(III) ions by the aldehyde. In turn the aldehyde is oxidised to the corresponding carboxylic acid.
The electron-half-equation for the reduction of dichromate(VI) ions is:
- 3RCHO + Cr2O7 -2 + 8H+ ____} 3RCOOH + 2Cr+3 + 4H2O
What else can I help you with?
A organic compound with a ratio of one carbon atom to two hydrogen atoms to one oxygen atom is a?
Such common compound is Glucose C6H12O6 but most of the mono saccharides have same ratio.
What acids are formed when formaldehyde breaks down?
When formaldehyde breaks down, it can form formic acid and carbon monoxide. Formic acid is a carboxylic acid that can exist in both a gaseous and liquid form, and can lead to irritation in the respiratory system when inhaled. Carbon monoxide is a toxic gas that interferes with the body's ability to carry oxygen in the blood.
Formation of formaldehyde from methyl alcohol?
In the body this reaction is carried out by the enzyme alcohol dehydrogenase, the same enzyme that reduces ethyl alcohol to acetaldehyde: http://en.wikipedia.org/wiki/Alcohol_dehydrogenase This is main mechanism of methanol toxicity due to the tissue damage casued by the resulting formaldehyde. On the bench you can perform a variety of dehydrogenation reactions, usually catalysed by metal salts such as copper chromite. The industrial method involves passing methanol vapour over copper heated to 300C.
Main reason for the difference in boiling points of Methanal and Ethanal?
The main reason for the difference in boiling points between methanal (formaldehyde) and ethanal (acetaldehyde) is the difference in molecular weight and size. Ethanal has a larger molecular size and weight compared to methanal, which leads to stronger intermolecular forces such as van der Waals forces, resulting in a higher boiling point for ethanal.
What is the best route for synthesis of pyridine-4-acetaldehyde?
What is the best route for synthesis of pyridine-4-acetaldehyde?
Why is formaldehyde is more reactive than acetaldehyde?
Formaldehyde is more reactive than acetaldehyde because it has a higher electrophilicity due to the lack of alkyl groups providing steric hindrance. This makes formaldehyde a better electrophile and more prone to reacting with nucleophiles compared to acetaldehyde. Additionally, the lack of alkyl groups in formaldehyde results in a greater stabilization of the transition state during reactions.
What is the distinguish between?
how can you distinguish between them
Why do you use ethanol in intravenous infusion form to treat methanol intoxication?
The liver metabolizes the ethanol into acetaldehyde in preference to metabolizing the methanol. That slows the buildup of formaldehyde -- with luck, enough to prevent it from building to a lethal level.
What is the difference between phenolic resin and urea formaldehyde resin?
Phenolic resin is made by the reaction between phenol and formaldehyde, whereas urea formaldehyde resin is made by the reaction between urea and formaldehyde. Phenolic resin offers higher heat resistance and better moisture resistance compared to urea formaldehyde resin. Urea formaldehyde resin is typically more cost-effective and has better flexibility than phenolic resin.
Distinguish between accounting and book keeping?
distinguish between book keeping and accounting
A organic compound with a ratio of one carbon atom to two hydrogen atoms to one oxygen atom is a?
Such common compound is Glucose C6H12O6 but most of the mono saccharides have same ratio.
Define and distinguish between entries on the books and entries on the workpapers and explain why such an entries on the books and on the workpapers are required in the consolidation process?
what is distinguish between bookkeeping and accounting? what is distinguish between bookkeeping and accounting? what is distinguish between bookkeeping and accounting?
Are acetone and acetaldehyde isomers?
No, acetone (CH3COCH3) and acetaldehyde (CH3CHO) are not isomers. Acetone is a ketone, while acetaldehyde is an aldehyde. They have different functional groups and structural arrangements.
What is Distinguish Between Accounting Convention And Aoncept?
Distinguish Between Accounting Convention And Aoncept
What is difference between acetylene and formaldehyde?
Oxygen is a chemical element, acetylene is an organic chemical compound.
What is the reaction between formaldehyde and sulfuric acid?
The reaction between formaldehyde and sulfuric acid forms methylene bisulfate. This is a reversible reaction that can also produce bisulfite ions and water as byproducts.
The placement of the double bond goes between which two atoms in this formaldehyde molecule?
formaldehyde, methanal, H2C=O (There is only one possibility here in formaldehyde, because there is NEVER a double bond with a H-atom!, and that leaves only: between C and O) hydrogens are unable to have double bonds because the each only have a single electron to share. The above commenter is correct with the placement of the double bond.
