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Chapter 15: Problem 321

Give structures of compounds \(\mathrm{A}, \mathrm{B}\) and \(\mathrm{C}\) : ethyl oxalate \(+\) ethyl acetate + sodium ethoxide, then \(\mathrm{H}^{+} \rightarrow \mathrm{A}\left(\mathrm{C}_{8} \mathrm{H}_{20} \mathrm{O}_{5}\right)\) \(\mathrm{A}+\) ethy 1 bromoacetate \(+\mathrm{Zn}\), then \(\mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{B}\left(\mathrm{C}_{12} \mathrm{H}_{20} \mathrm{O}_{7}\right)\) \(\mathrm{B}+\mathrm{OH}^{-}+\) heat, then \(\mathrm{H}^{+} \rightarrow \mathrm{C}\left(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}\right)\), citric acid.

Short Answer

Expert verified
In this series of reactions: 1) Sodium ethoxide deprotonates ethyl acetate, which then attacks ethyl oxalate, resulting in Compound A (\(C_{8}H_{20}O_{5}\)). 2) Ethyl bromoacetate reacts with zinc forming a carbanion that attacks the carbonyl carbon of compound A, giving Compound B (\(C_{12}H_{20}O_{7}\)). 3) Heating compound B with hydroxide, followed by acidification, results in the formation of citric acid (Compound C, \(C_{6}H_{8}O_{7}\)).

Step by step solution

01

React ethyl oxalate, ethyl acetate, and sodium ethoxide

Sodium ethoxide would act as a base and remove the acidic hydrogen from ethyl acetate, generating a resonance-stabilized enolate, which then attacks the carbonyl of ethyl oxalate. The result of this reaction is Compound A with a molecular formula of \(C_{8}H_{20}O_{5}\).
02

React Compound A, ethyl bromoacetate and Zn

Ethyl bromoacetate can be considered as a carbonyl compound with a good leaving group (bromo group). When it reacts with zinc, it forms a carbanion. This carbanion is a strong nucleophile. It can react with compound A as carbonyl compound by attacking its carbonyl carbon to eliminate ethoxide anion. This gives us compound B, with a molecular formula of \(C_{12}H_{20}O_{7}\).
03

React Compound B with an Hydroxide Ion and heat, then add an acid

Heating compound B with hydroxide would form a carboxylate ion by losing a molecule of ethanol. Then adding \(H^+\) to the resulting solution will give citric acid (Compound C), with a molecular formula of \(C_{6}H_{8}O_{7}\). It's worth noting that citric acid is a well-known organic compound, and its structure is widely accepted. This can help in reassuring that the reactions conducted in steps 1, 2 and 3 are feasible as they lead to a known compound with the specified molecular formula.

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Most popular questions from this chapter

The following experimental observations have been reported: [1]) t-Buty1 chloride was added to lithium metal in dry ether at \(35^{\circ}\). A vigorous reaction ensued with evolution of hydrocarbon gases. After all the lithium metal was cosumed, the mixture was poured onto Dry Ice. The only acidic product which could be isolated (small yield) was 4,4 -dimethylpentanoic acid. 2) t-Buty1 chloride was added to lithium metal in dry ether at \(-40^{\circ}\). After all the lithium had reacted, the mixture was carbonated and gave a good yield of trimethylacetic acid. 3) t-Buty1 chloride was added to lithium metal in dry ether at \(-40^{\circ}\). After all the lithium was gone, ethylene was bubbled through the mixture at \(-40^{\circ}\) until no further reaction occurred. Carbonation of this mixture gave a good yield of 4, 4 -dimethylpentanoic acid. a) Give a reasonably detailed analysis of the results obtained and show as best you can the mechanisms involved in each reaction. b) Would similar behavior be expected with methy1 chloride? Explain. (c) Would you expect that any substantial amount of \(6,6-\) dimethytheptanoic acid would be found in (3) (above)? Explain.

Write balanced equations for the preparation of each of the following organometallic compounds by two different reactions starting from suitable alky1 halides and inorganic reagents. Specify reaction conditions and solvents. In each case, indicate which method of preparation you would prefer from standpoints of yield, convenience, etc. (a) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{Zn}\) (c) \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2}\right)_{4} \mathrm{~Pb}\) (b) \(\mathrm{CH}_{3} \mathrm{MgCl}\) (d) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CHLi}\)

Excess methylmagnesium iodide and \(0.1776 \mathrm{~g}\) of compound A of formula \(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O}_{3}\) Sreact to give \(84.1 \mathrm{cc}\) of methane collected over mercury at \(740 \mathrm{~mm}\) and \(25^{\circ} \mathrm{C}\). How many active hydrogens does compound A possess? Suggest a possible structure for the compound given that the infrared spectrum shows no carbonyl absorption and the n.m.r. spectrum shows only three types of hydrogen with areas in the ratio of \(1: 2: 2\).

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