(a)
Interpretation:
When the given compound is heated, ethene gas is evolved and a product with the formula C14H8O2 is formed. The structure of C14H8O2 is to be drawn from the given data.
Concept introduction:
The Diels-Alder reaction is reversible at high temperature, and this process is called a retro Diels-Alder reaction. The mechanism for this reaction is as the reverse of a Diels-Alder mechanism i.e. the entire six-membered ring is break-down into the corresponding diene and the dienophile. The aromatic proton given signal range from 7 to 9 ppm in 1H NMR spectrum and that is for 13C NMR spectrum the signal range is 120 to 140 ppm.
Answer to Problem 24.82P
The structure of C14H8O2 is
Explanation of Solution
The given compound is
So when this compound is heated, ethene gas is evolved and a product with formula C14H8O2 is formed. Let’s focus on the formula of the product. First, calculate the degree of unsaturation for the product.
DBE =2C - H - X + N + 22
= 2 × 14 - 8 + 22
= 11 (so the compound is aromatic and contains more than one benzene ring)
The signal in 1H NMR the spectrum between 7 and 9 ppm suggests that the compound must be aromatic and more deshielding is due to the presence of carbonyl groups on the benzene ring. The 13C NMR spectrum also gives the signal in the aromatic region and only four signals in 13C NMR spectrum suggest that the product is highly symmetric. Thus the product must be aromatic. The signal at 185 ppm corresponds to the carbonyl carbons. Now focusing on the given compound, which on heating, ethene gas is evolved and the aromatic product with molecular formula C14H8O2 is formed. Thus the retro Diels-Alder reaction may take place as shown below:
The product of the retro Diels-Alder reaction is also aromatic and matched with the given spectra and also ethene gas is evolved. so the above product is the correct one.
When the given compound is heated, ethene gas is evolved and a product with the formula C14H8O2 is formed. The structure of C14H8O2 is drawn from the given data.
(b)
Interpretation:
When the given compound is heated, ethene gas is evolved and a product with the formula C14H8O2 is formed. The mechanism is to be drawn that accounts for its formation.
Concept introduction:
The Diels-Alder reaction is reversible at high temperature and this process is called a retro Diels-Alder reaction. The mechanism for this reaction is as the reverse of a Diels-Alder mechanism i.e. the entire six-membered ring is broken down into the corresponding diene and the dienophile. The aromatic proton given signal range from 7 to 9 ppm in 1H NMR the spectrum and that is for 13C NMR spectrum the signal range is 120 to 140 ppm.
Answer to Problem 24.82P
The mechanism for the given reaction is
Explanation of Solution
The given compound is
So when this compound is heated, ethene gas is evolved and product with formula C14H8O2 is formed. Let focus on the formula of the product. First, calculate the degree of unsaturation for the product.
DBE =2C - H - X + N + 22
= 2 × 14 - 8 + 22
= 11 (so the compound is aromatic and contains more than one benzene ring)
The signal in 1H NMR spectrum between 7 and 9 ppm suggests that the compound must be aromatic and more deshielding due to the presence of carbonyl groups on the benzene ring. The 13C NMR spectrum also gives the signal in the aromatic region, and the signal at 185 ppm corresponds to the carbonyl carbons, and only four signals in 13C NMR spectrum suggest that the product is highly symmetric. Thus the product must be aromatic. Now focusing on the given compound, which on heating, ethene gas is evolved and the aromatic product with molecular formula C14H8O2 is formed. Thus the retro Diels-Alder reaction may take place as shown below:
The product of the retro Diels-Alder reaction is also aromatic and matched with the given spectra and also ethene gas is evolved. So the above product and the mechanism (retro Diels-Alder mechanism) is the correct one.
When the given compound is heated, ethene gas is evolved and a product with the formula C14H8O2 is formed. The mechanism is drawn that accounts for its formation.
(c)
Interpretation:
When the given compound is heated, ethene gas is evolved and a product with the formula C14H8O2 is formed. The main driving force that favours the product in the given reaction is to be stated.
Concept introduction:
The Diels-Alder reaction is reversible at high temperature and this process is called a retro Diels-Alder reaction. The mechanism for this reaction is as the reverse of a Diels-Alder mechanism i.e. the entire six-membered ring is break-down into the corresponding diene and the dienophile. The aromatic proton given signal range from 7 to 9 ppm in 1H NMR spectrum and that is for 13C NMR spectrum the signal range is 120 to 140 ppm.
Answer to Problem 24.82P
The main driving force that favours the product in the given reaction is the formation of a more stable aromatic compound.
Explanation of Solution
The given reaction is
It is noticed that the starting material in the given reaction is overall non-aromatic and also possesses strain due to middle ethylene groups on both sides, but the product is aromatic and strain-free one. Since aromatic compounds are more stable than the non-aromatic compounds this is a key state and the main driving force for the given reaction.
When the given compound is heated, ethene gas is evolved and a product with the formula C14H8O2 is formed. The main driving force that favours the product in the given reaction is stated.
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Chapter 24 Solutions
ORGANIC CHEM PRINC & MECH (BUNDLE)
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