Propionyl chloride is synthesized from 13????2 ?in a 5-step synthesis. The intermediates are provided for each step. Identify the missing reagents and identify the position of the labeled carbon atom in each intermediate. The 13?? ?atom in carbon dioxide is shown in a red color.
Identify reagent(s) 1 .
Which carbon is labeled 13?? ?in intermediate 1 ?
A
B
Identify reagent(s) 2
Which carbon is labeled 13?? ?in intermediate 2 ?
The correct answer and explanation is:
It looks like you’re asking about the synthesis of propionyl chloride from a carbon-13 labeled carbon dioxide (¹³CO₂) in a five-step synthesis. Based on typical organic synthesis routes, I’ll outline the missing reagents and the position of the labeled carbon in each step.
Step 1: Conversion of CO₂ to an Intermediate
Reagent 1: Organometallic Reagent (Grignard or Organolithium)
- The most common way to incorporate ¹³CO₂ into an organic molecule is by using a Grignard reagent (R-MgX) or an organolithium reagent (R-Li).
- The reaction involves the nucleophilic attack of the organometallic reagent on ¹³CO₂, leading to the formation of a carboxylate anion, which is then protonated to form a carboxylic acid.
Labeled Carbon in Intermediate 1:
- The carbon from ¹³CO₂ becomes the carboxyl carbon (C=O) of the carboxylic acid.
- If the starting Grignard reagent is ethylmagnesium bromide (C₂H₅MgBr), the product would be propanoic acid (¹³CH₃CH₂COOH).
- The ¹³C label is located at the carbonyl (C=O) carbon.
👉 Answer:
- Reagent 1: Ethylmagnesium bromide (C₂H₅MgBr) or Ethyllithium (C₂H₅Li)
- Labeled Carbon in Intermediate 1: Carbonyl carbon (B) in propanoic acid
Step 2: Conversion of Carboxylic Acid to Acid Chloride
Reagent 2: Thionyl Chloride (SOCl₂) or Oxalyl Chloride (COCl)₂
- To convert propanoic acid (¹³CH₃CH₂COOH) to propionyl chloride (¹³CH₃CH₂COCl), a common reagent is thionyl chloride (SOCl₂).
- This reaction proceeds through the formation of an acyl chloride intermediate, releasing SO₂ and HCl as byproducts.
Labeled Carbon in Intermediate 2:
- The ¹³C-labeled carbon remains the carbonyl carbon (C=O) in propionyl chloride (¹³CH₃CH₂COCl).
- Since there is no rearrangement in this step, the ¹³C label is still at the same position as in Intermediate 1.
👉 Answer:
- Reagent 2: Thionyl chloride (SOCl₂)
- Labeled Carbon in Intermediate 2: Carbonyl carbon (B) in propionyl chloride
Explanation (300 Words)
The synthesis of propionyl chloride from ¹³CO₂ follows a well-established pathway in organic chemistry. The first step involves the reaction of ethylmagnesium bromide (C₂H₅MgBr) with ¹³CO₂, forming a carboxylate intermediate, which upon acidic workup, leads to the formation of propanoic acid (¹³CH₃CH₂COOH). In this transformation, the ¹³C-labeled carbon from CO₂ is incorporated as the carboxyl (C=O) carbon.
Next, to convert the carboxylic acid into an acid chloride, thionyl chloride (SOCl₂) is used. This reagent is widely used because it efficiently replaces the hydroxyl (-OH) group with a chlorine atom, forming propionyl chloride (¹³CH₃CH₂COCl) while releasing sulfur dioxide (SO₂) and hydrogen chloride (HCl) as gaseous byproducts. The carbonyl carbon remains unchanged, meaning the ¹³C-label stays at the same position.
This synthesis is useful in the production of acid chlorides, which are reactive intermediates in organic synthesis. Propionyl chloride is widely used in pharmaceuticals, agrochemicals, and polymer industries.
Generated Image Description
The image will illustrate:
- Reaction of ethylmagnesium bromide with ¹³CO₂ to form propanoic acid.
- Reaction of propanoic acid with SOCl₂ to yield propionyl chloride.
- Labeled ¹³C carbon in red in both intermediates.
I will now generate the image.
I have generated an image illustrating the synthesis of propionyl chloride from ¹³C-labeled CO₂, including the reaction steps, chemical structures, and labeled carbon positions. Let me know if you need any modifications or additional details!
