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Aldehydes Compounds with general formula RCHO and ketones are compounds with the general formula RRCO. Both groups have a carbonyl group that performs similar reactions. In fact, the chemistry of these compounds is the chemistry ofthe carbonyl functional group.
Due to the electron and spatial factors, aldehydes are more easily oxidized to ketones and are more reactive than ketones in increasing the nucleolifilia. Identification of these compounds is possible by the characteristic reactions of the carbonyl functional group.
Chemical properties of aldehyde and ketone
The most important interactions that aldehyde and ketones are involved in are:
1- Electron-induced electrochemical attack on Oxygen The carbonyl group increases the carbon-carbon positive carbon density, which ultimately increases the acidity of the carbonyl alpha carbon protonates.
2. Nuclear attack on the carbon dioxide of the second carbon dioxide group
Aldehydes and Ketones Identification Tests
There are several tests for the identification of aldehydes and ketones that can be tested for 2 and 4-di-nitrophenylhydrazine, sodium bisulfide test, talenz test, benech test, fosin test, chromic acid test, iodoform test. .
Test 2 and 4 - Di-nitro-phenyl hydrazine:
This test is the most prominent test for the detection of aldehydes and ketones. Aldehydes and ketones with a reagent 2 and 4-di-nitro-phenyl hydrazine form a yellow to orange deposit (red).
Aldehyde and ketones that have a carbonaceous conjugate and are unsaturated are orange (red), i.e. with higher wavelengths
Note: In addition to identifying aldehyde or ketones, this test is also one of the derivatives of these compounds, since the formation of the sediment is polarized, flattened and heavierthan aldehyde and ketone
.
Preparation Method for Reagents 2 and 4 Dinitrophenylhydrazine:
Dissolve
1 g 2 and 4 di-nitro-phenyl hydrazine in 5 ml of concentrated sulfuric
acid and carefully add 7 ml of water and 25 ml of 95% ethanol solution.
After stirring the solution vigorously, , We straighten it to separate the created sediment.
Error factors:
Some Allyl Derivatives Alcohols may be converted to oxygen by air to
ketones and ultimately produced in the form of a sediment reagent. For
example: cinnamines-di-phenyl-krananol
So, in general, if the alcohol is easily oxidized by oxygen and
converted to aldehyde and ketone, then it may be possible for us to make
a mistake in this test.
Vitamin A1 is also one of the compounds that produces this sediment reagent.
Some ketones do not create sediment with this reagent. For example:
octinum ketone-dimethyl ketone, which produces yellow or orange-yellow
sediment.
Physical characteristics of this test: color change and sedimentation
Sodium Bisulfite Test:
Most aldehydes produce this milky-colored test. Obtaining this milk
product requires a lot of care, and the stated amounts must be fully met
to achieve the desired result from this test.
In the form below, the reaction of an aldehyde or ketone with sodium sulfite is shown
Error factors
This
test is susceptible because sodium bisulfite (the reagent) dissolves in
water, so it may not be possible to produce a milk color of the product
in water, or it may not be possible to dissolve the aldehyde that we
want to test in water, or the sodium bisulfite product that exists It comes in fully soluble water. None of these states easily answers this test.
Solution:
In order to minimize the mistake, make a blue solution of alcohol so
that the sodium sulfite can precipitate slightly, but care should be
taken to remove the sediment by decanting or smoothing, so that it does
not pass into the aldehyde container. That is, with saturated solution Sodium bisulfite alcohol test.
There may be compounds that produce the same result without causing the aldehyde or ketone, causing the dye to appear.
Physical properties of the test: the formation of milky sediment
TALANS or TOLNES TESTING:
All aldehydes and light ketones respond positively to this test. In
other words, the Talens test is used to detect aldehydes from ketones.
Aldehydes are tested in response to the Thalene reagent (Tolls), producing a silver mirror in the tube wall
Preparation Method for Thalanges:
Dissolve
3 g of silver nitrate in 30 ml of water, then mix 1 ml of the resulting
solution with 1 ml of 10% solution of the solution to form a silver
oxide deposit (Note: If we do not make it, because the silver nitrate is
completely The solution is not prepared to react with aldehyde.
Then
add drops of concentrated ammonia solution to dissolve the silver oxide
deposition. Now the reactant is ready for testing. (Note: if you add a
lot of ammonia, the resulting complex will become so stable that it is
no longer able to release the + Ag to react with Does not have aldehyde.)
Note:
Thalassium reagent should be used while consumed and the remainder
disposed of in a dishwasher. As the solution is stored, there is the
possibility of formation of Ag2C2N2O2 explosive deposits. This sediment is a mixture of silver nitride (Ag3N) and silver azide (AgN3).
Error factors:
1. If the test tube is not completely clean, silver does not form in
the form of a silver mirror in the test tube wall, and appears as a
deposition or black suspension.
2. Some simple ketones, such as acetone and methyl ethyl ketone, also respond positively to this test.
3. There are compounds that are more convenient than aldehyde.
Physical properties of the test: the formation of a silver deposit on the interior of the container
Benedict Test:
This reagent is called the American chemist (Stanley Rossiter Benedict).
In this test, copper is used to detect sulfur-free aliphatic
(non-aromatic) aldehydes (such as sugary compounds) and alpha-hydroxy
ketones.
In fact, Cu + 2 can oxidize aldehyde or ketones and tu into Cu + 1, which is red.
Chemical properties
RCHO + 2Cu(citrate)2+ → RCOOH + Cu2O(s) + H2O
Physical properties
Creates a red, yellow, green color that depends on the amount of sugar
Presenting Benedict Method:
Dissolve 173 g sodium citrate and 100 g sodium carbonate anhydrous in 800 ml of water and add 850 ml by adding distilled water. In another container, dissolve 1.7 g of copper sulfate juice in 100 ml
of water and add the resulting solution to the citrate and carbonate
solution and add the final solution volume by adding one liter to the
solution.
Chemical error:
Any regenerator that can convert bivalent copper to a copper is a
color that creates complexity in this test. For example:
phenylhydrazines
Physical error:
Copper sulfate is not dissolved in organic environments because it is an inorganic salt !!
To solve this problem, we introduce an organic anion (sodium citrate)
that can replace copper cation and sit instead of sulfate. Because it
dissolves itself in the organic environment, copper can also enter the
organic environment.
To improve this, we can make the environment alkaline to increase the chance of copper sulfate in the organic environment.
Physical properties of the test: the formation of red, yellow, green deposits whose color depends on the amount of sugar
Fushin Test:
This test responds to aldehydes and light ketones.
In the fushin test, the reagent should not be heated, and the test
solution should not be alkaline. When the test is performed on a fog,
it's better to use a known aldehyde as a control.
Foscin Reagent Preparation Method:
Dissolve
0.5 g of pure pure foshin (rosaniline hydrochloride) in 500 ml of
distilled water and make up the solution, make 500 ml of distilled water
with sulfur dioxide, saturate with Fushin solution completely We mix and spend for one night. This method produces a nasty and sensitive design.
Error factors
Due to the high sensitivity of the foshine reagent, high levels of sulfuric acid reduce the sensitivity of the reagent.
Invalid use of small quantities of reagents
Film 2 & 4 Diphenylhydrazine:
http://www.aparat.com/v/n8IrQ
References :
http://ikiu-chemicalstudent.blogfa.com/post/7
http://academics.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Appendix/ClassificationTests/aldehyde_ketone.htm
Identification of ٍٍEsters
Physical and Chemical Properties of Esters
1) The boiling temperature of the ethers is much lower than the boiling point of the corresponding acids. Reason: With the substitution of the RO group - with HO - the possibility of hydrogen bonding is eliminated. Thus, the molecules of the ester are simple molecules.
2) Esters are more stable than heat in the heat.
3. Due to the lack of hydrogen bonding of esters in water, organic solvents are better than acids.
4. Starches are considered to be the best organic solvents.
5. Styles are aromatic compounds and most fruits are found in essential oils
Preliminary testing
Dissolve 4 drops of unknown liquid in 3 ml of water or ethanol and add 3 to 2 drops of 5% friction chloride solution in water
Physical property
If the primary color does not intensify, then the negative is negative and we can test hydroxamid. But if the color is orange, red, blue, purple, purple, green or red, then the test is positive and the hydroxamid test is useless
Hydroxamic acid test
R-CO-OR' + H2N-OH -> R-CO-NH-OH + R'-OH
Esters react with hydroxylamine in the presence of sodium hydroxide to form the sodium salt of the corresponding hydroxamic acid. On acidification and addition of ferric chloride the magenta-coloured iron (III) complex of the hydroxamic acid is formed
It is always advisable to ensure that an unknown compound does not give a colour with iron (III) chloride before carrying out the hydroxamic acid test
Physical property
The color of the red solution is red
Chemical properties
When the esters are heated with hydroxylamine, they converge to the hydroxamic acid Hydroxamic acids form stable and colored complexes with ionic ferric
complication errors
A number of acids are tested positive.
. Initial Nitro Compounds and Compounds, Amides A number of amides and more nitriles and aldehydes are hydrogen-free alpha to test.
. Positive test for amide is soluble in red, the negative test is yellow and brown is brown containing sediment.
. The basic test must be performed before the main test. If you change color with ferric chloride, the main test can not be done because it may be in the impurities that react with the ferric chloride and give it a red color
Mechanism
Chromatography...
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