Q1. What will be formed when propanone reacted with sodium hydrogensulphite?
There is white precipitate is the resulting solution . Is it sodium carbonate?
Q2. What are the difference in the products bewteen the reaction of ethanal and propanone reacting with 2,4-dinitrophenylhydrazine?
The resulting solution are both yellow and orange precipitate is formed . It seems that there are some different in the shape of precipitate.
Q3. What is the polymer formed when ethanal reacted with sodium hydroxide solution?
Q4. What will be formed when ethanal reacted with acidified dichromate(VI) ?
Why is the resulting solution green ?
Q5. What will be formed when propanone reacted with Fehling's solution?The resulting solution is yellow and green precipitate is formed . Is that precipitate copper carbonate?
Q6.What are the difference in products between the reaction of ethanal and propanone reacting with iodine solution and sodium hydroxide solution ?The resulting solution of ethanal one is orange while the other is very pale yellow or nearly colorless.Both of them give yellow precipitate . Are the precipitates the same?
Q7. Which reagent should i use to test for carbonyl compound?
Sra
A1. When propanone (also known as acetone) reacts with sodium hydrogensulphite, sodium bisulphite adduct of propanone is formed. This adduct is a white precipitate that can be separated from the resulting solution.
To determine if the white precipitate is sodium carbonate, you can perform a simple test. Add a small amount of dilute hydrochloric acid to the white precipitate. If it effervesces (produces bubbles), then it is likely sodium carbonate. Another way to confirm the presence of carbonate ions is by performing a flame test. When sodium carbonate is heated, it will emit a yellow flame.
A2. The reaction of ethanal and propanone with 2,4-dinitrophenylhydrazine (DNPH) forms compounds known as hydrazones. Both ethanal and propanone form yellow precipitates when reacted with DNPH, but there might be subtle differences in the shape or appearance of the precipitates. These differences can be attributed to the different molecular structures of ethanal and propanone, which affect the arrangement of the resulting hydrazones.
To further distinguish between the two compounds, you can collect the precipitates and perform melting point tests. Each compound will have a unique melting point range, allowing for identification and differentiation.
A3. Ethanal (also known as acetaldehyde) reacts with sodium hydroxide solution to form a polymer known as poly(acetaldehyde). This polymerization reaction occurs via the aldol condensation reaction, where two ethanal molecules combine to form a larger molecule with repeating units.
A4. When ethanal reacts with acidified dichromate(VI), it undergoes oxidation to form ethanoic acid (also known as acetic acid). The resulting solution is green in color due to the presence of chromium ions in the Cr(VI) state.
The green color is a characteristic of chromium compounds, and it arises from the absorption of certain wavelengths of light by the compound's electronic structure. The specific shade of green can vary depending on factors such as the concentration and pH of the solution.
A5. When propanone reacts with Fehling's solution (a test for reducing sugars), a redox reaction occurs, leading to the formation of a yellow-orange precipitate of cuprous oxide. The resulting solution remains yellow.
The yellow and green precipitate you mentioned is not copper carbonate but cuprous oxide. The color can vary depending on the concentration and conditions of the reaction.
A6. The reactions of ethanal and propanone with iodine solution and sodium hydroxide solution give different products.
Ethanal reacts with iodine to form a yellow-orange precipitate of iodoform (CHI3), giving the solution an orange color. On the other hand, propanone reacts with iodine to form a pale yellow or nearly colorless precipitate of triiodomethane (CHI3), which does not significantly affect the color of the solution.
Although both reactions give yellow precipitates, the precipitates are not the same. Ethanal gives iodoform, while propanone gives triiodomethane. You can further confirm the identity of the precipitates using tests such as melting point determination.
A7. To test for a carbonyl compound, you can use reagents like Tollens' reagent (ammoniacal silver nitrate), Fehling's solution, or 2,4-dinitrophenylhydrazine (DNPH).
Tollens' reagent is used to test for aldehydes specifically. Aldehydes will reduce the silver ions in the reagent to form a silver mirror on the inside of the test tube.
Fehling's solution is also used to test for aldehydes and reduces them to form a red precipitate of copper(I) oxide.
DNPH is a commonly used reagent to test for both aldehydes and ketones. It forms colored precipitates (hydrazones) with carbonyl compounds, which can be used for identification.
The choice of reagent depends on the type of carbonyl compound being tested and the specific identification required.