9. Cubane and its derivatives have been considered for use as explosives and as materials for energy storage. The heat of combustion of cubane is = -1156.0 kcal/mol. The heat of combustion of your average, strainless methine group is -124 kcal/mol. Calculate the strain energy of cubane. What structural features contribute to the molecule's strain? H-C cubane a methine group
Carbohydrates
Carbohydrates are the organic compounds that are obtained in foods and living matters in the shape of sugars, cellulose, and starch. The general formula of carbohydrates is Cn(H2O)2. The ratio of H and O present in carbohydrates is identical to water.
Starch
Starch is a polysaccharide carbohydrate that belongs to the category of polysaccharide carbohydrates.
Mutarotation
The rotation of a particular structure of the chiral compound because of the epimerization is called mutarotation. It is the repercussion of the ring chain tautomerism. In terms of glucose, this can be defined as the modification in the equilibrium of the α- and β- glucose anomers upon its dissolution in the solvent water. This process is usually seen in the chemistry of carbohydrates.
L Sugar
A chemical compound that is represented with a molecular formula C6H12O6 is called L-(-) sugar. At the carbon’s 5th position, the hydroxyl group is placed to the compound’s left and therefore the sugar is represented as L(-)-sugar. It is capable of rotating the polarized light’s plane in the direction anticlockwise. L isomers are one of the 2 isomers formed by the configurational stereochemistry of the carbohydrates.
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Cubane consists of a cubic structure, with each corner representing a carbon atom. This shape is highly unusual in organic chemistry for such small molecules because of the angles involved.
2. **Methine Group:**
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A methine group consists of one carbon atom bonded to three other groups and one hydrogen. It is typically unstrained in its standard tetrahedral configuration.
**Explanation:**
Cubane features significant ring strain due to its cubic structure, forcing bond angles to 90° instead of the more natural 109.5° for sp3 hybridized carbons. This deviation from ideal angles results in a high strain energy, contributing to both its high heat of combustion and potential use in high-energy applications.
To calculate the strain energy of cubane, compare the total heat of combustion of cubane with the combustion heat of an equivalent number of strain-free methine groups:
\[ \text{Strain Energy of Cubane} = \text{Heat of Combustion of Cubane} - (8 \times \text{Heat of Combustion of a Methine Group}) \]
Given:
\[ \text{Heat of Combustion of Cubane} = -1156.0 \text{ kcal/mol} \]
\[ \text{Heat of Combustion of Methine Group} = -124 \text{ kcal/mol} \]
Calculating:
\[ \text{Strain Energy of Cubane} = -1156.0 \text{ kcal/mol} - (8 \times -124 \text{ kcal/mol}) \]
\[ \text{Strain Energy of Cubane} = -1156.0 \text{ kcal/mol} - (-992 \text](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fa44093f9-865e-42e2-9761-7238b47b32ab%2F769e64bd-6963-4666-a76e-6b6a3b1e3d80%2Fdofmqx7_processed.jpeg&w=3840&q=75)
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