Self-condensation of acetone is a possible side reaction for the aldol condensation (Reaction 1). Draw the structure of this side product. How is this side reaction minimized in our procedure written below? Reaction 1 - Experimental Procedure: In a clean, small Erlenmeyer flask, combine your unknown aromatic aldehyde (350 μL (400 mg if it is a solid)), 95% ethanol (2.0 mL), and 5 N aqueous sodium hydroxide (0.6 mL). Swirl to mix, and then add acetone (100 μL). Stir/swirl vigorously for 30 minutes, until precipitation is complete. If no precipitate forms after 15 minutes, heat the Erlenmeyer flask gently in on the sand bath in the hood for 15 minutes, and then allow it to cool to room temperature. Whether heated or not, cool your Erlenmeyer flask in an ice bath for 10 minutes to ensure complete crystallization. Collect the product by vacuum filtration. (If you do not have any solid at this point, evaporate all solvent in the sand bath. Recrystallize if solid residue is obtained; otherwise stop here and analyze the liquid residue.) Wash the crude product consecutively with ice-cold 95% ethanol (1 mL), 10% acetic acid (1 mL), and again with ice-cold 95% ethanol (1 mL). Air dry your sample.
Reactive Intermediates
In chemistry, reactive intermediates are termed as short-lived, highly reactive atoms with high energy. They rapidly transform into stable particles during a chemical reaction. In specific cases, by means of matrix isolation and at low-temperature reactive intermediates can be isolated.
Hydride Shift
A hydride shift is a rearrangement of a hydrogen atom in a carbocation that occurs to make the molecule more stable. In organic chemistry, rearrangement of the carbocation is very easily seen. This rearrangement can be because of the movement of a carbocation to attain stability in the compound. Such structural reorganization movement is called a shift within molecules. After the shifting of carbocation over the different carbon then they form structural isomers of the previous existing molecule.
Vinylic Carbocation
A carbocation where the positive charge is on the alkene carbon is known as the vinyl carbocation or vinyl cation. The empirical formula for vinyl cation is C2H3+. In the vinyl carbocation, the positive charge is on the carbon atom with the double bond therefore it is sp hybridized. It is known to be a part of various reactions, for example, electrophilic addition of alkynes and solvolysis as well. It plays the role of a reactive intermediate in these reactions.
Cycloheptatrienyl Cation
It is an aromatic carbocation having a general formula, [C7 H7]+. It is also known as the aromatic tropylium ion. Its name is derived from the molecule tropine, which is a seven membered carbon atom ring. Cycloheptatriene or tropylidene was first synthesized from tropine.
Stability of Vinyl Carbocation
Carbocations are positively charged carbon atoms. It is also known as a carbonium ion.
Self-condensation of acetone is a possible side reaction for the aldol condensation
(Reaction 1). Draw the structure of this side product. How is this side reaction minimized
in our procedure written below?
Reaction 1 - Experimental Procedure: In a clean, small Erlenmeyer flask, combine your unknown
aromatic
sodium hydroxide (0.6 mL). Swirl to mix, and then add acetone (100 μL). Stir/swirl vigorously for
30 minutes, until precipitation is complete. If no precipitate forms after 15 minutes, heat the
Erlenmeyer flask gently in on the sand bath in the hood for 15 minutes, and then allow it to cool
to room temperature. Whether heated or not, cool your Erlenmeyer flask in an ice bath for 10
minutes to ensure complete crystallization. Collect the product by vacuum filtration. (If you do
not have any solid at this point, evaporate all solvent in the sand bath. Recrystallize if solid
residue is obtained; otherwise stop here and analyze the liquid residue.) Wash the crude product
consecutively with ice-cold 95% ethanol (1 mL), 10% acetic acid (1 mL), and again with ice-cold
95% ethanol (1 mL). Air dry your sample.
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