The ketone whose ¹H NMR spectrum is shown here was obtained as the product of an acetoacetic ester synthesis. What alkyl halide was used in the synthesis?
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Verified step by step guidance

1. Step 1: Analyze the molecular formula provided in the image, C₅H₁₀O, which indicates the compound is a ketone with five carbons, ten hydrogens, and one oxygen atom.
2. Step 2: Examine the ¹H NMR spectrum. The spectrum shows three distinct signals: a singlet at approximately 2.1 ppm (3H), a quartet at approximately 2.4 ppm (2H), and a triplet at approximately 1.0 ppm (3H). These signals correspond to different proton environments in the molecule.
3. Step 3: Interpret the singlet at 2.1 ppm (3H). This signal is characteristic of a methyl group directly attached to a carbonyl group (CH₃-C=O), which is consistent with the ketone functional group.
4. Step 4: Analyze the quartet at 2.4 ppm (2H) and the triplet at 1.0 ppm (3H). These signals suggest the presence of an ethyl group (-CH₂-CH₃) attached to the molecule. The quartet corresponds to the CH₂ group adjacent to the carbonyl group, and the triplet corresponds to the CH₃ group further away.
5. Step 5: Based on the acetoacetic ester synthesis mechanism, the alkyl halide used must introduce the ethyl group into the molecule. Therefore, the alkyl halide used in the synthesis is ethyl bromide (CH₃CH₂Br).

Key Concepts

Acetoacetic Ester Synthesis

Acetoacetic ester synthesis is a method for synthesizing ketones through the reaction of an acetoacetic ester with an alkyl halide. This process involves the formation of a β-keto ester, which can be hydrolyzed and decarboxylated to yield the desired ketone. Understanding this synthesis is crucial for identifying the starting materials and the resulting products in organic reactions.

NMR Spectroscopy

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. In 1H NMR, the chemical environment of hydrogen atoms is analyzed, providing information about the number of hydrogen atoms, their connectivity, and the presence of functional groups. Peaks in the spectrum correspond to different hydrogen environments, which are essential for deducing the structure of the synthesized ketone.

Alkyl Halides in Organic Synthesis

Alkyl halides are organic compounds containing a carbon atom bonded to a halogen atom (F, Cl, Br, I). They are commonly used as electrophiles in nucleophilic substitution reactions, making them key reagents in organic synthesis. Identifying the specific alkyl halide used in the acetoacetic ester synthesis is critical for understanding the reaction pathway and the final structure of the ketone produced.