Concept explainers
(a)
Interpretation:
Without consulting tables or figures, answer the following questions: a thermal disrotatory electrocyclic reaction involving 12 electrons allowed or forbidden-the statement is to be verified.
Concept introduction:
Electrocyclic reactions are a pericyclic reaction which occur intramolecularly. These reactions will result in the formation of ring compounds under the influence of heat or light. Notably, in this process one new sigma bond is formed and one old π-bond is consumed. Intriguingly, the reverse ring opening electrocyclic reaction can also be possible to occur under the same reaction mechanism but in reverse manner. According to molecular orbital concepts, systems having 4n π electrons undergoes conrotatory ring closure is allowed and this ring closure is forbidden for systems having 4n + 2 π systems. Similarly, disrotatory closing of rings is forbidden for 4n π electrons and allowed for 4n + 2 π electron systems.
(b)
Interpretation:
a [8s + 4s] photochemical cycloaddition is allowed-the statement is to be verified.
Concept introduction:
The reactions in which the formation of cyclic product observed by combining two or more unsaturated molecules is called cyclo addition reaction. Besides, the net reduction of bond multiplicity is observed. Molecules having 4n π electrons is allowed under photochemical conditions and 4n +2 π electrons is allowed under thermal conditions.
(c)
Interpretation:
the HOMO of (Z)-3, 4-dimethyl-1, 3, 5-hexatriene symmetric or antisymmetric-the statement is to be verified.
Concept introduction:
The reactions in which the formation of cyclic product observed by combining two or more unsaturated molecules is called cyclo addition reaction. Besides, the net reduction of bond multiplicity is observed. Molecules having 4n π electrons is allowed under photochemical conditions and 4n +2 π electrons is allowed under thermal conditions.
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Organic Chemistry
- Propose a mechanism for the following cycloaddition reaction. Classify the reaction using the [m + n] classifications for cycloadditions. Draw the bonding molecular orbitals and identify the type of bonding present (supra - supra, antaraantara, or supra - antara). Identify if this reaction would proceed thermally or photochemically.arrow_forwardQuestion: Explain the basis for the Woodward-Hoffmann rules in predicting the stereochemistry of the products formed in pericyclic reactions. Specifically, how do these rules apply to electrocyclic reactions and cycloadditions?arrow_forwardCyclohexene reacts with bromine in the presence of NaI to yield -?arrow_forward
- Fill in the blanks in the following reactions. Include stereochemistry when relevant.arrow_forwardBirch reduction of 2-methoxynaphthalene gave a mixture of two isomeric compounds, each having the molecular formula C11H14O. Suggest reasonable structures for these compounds.arrow_forwardAddition of HBr to 3,3-dimethyl-1-butene gives a mixture of two isomeric alkyl bromide products. Please daw structures for the two products, and give a mechanistic explanation for their formation.arrow_forward
- Solve the chloronation reactions and show stereochemistry.arrow_forwardHow many possible monoborminated products including stereoisomers would you expect for the reaction of 2,3-dimethylpentane with Br2 in the presence of light? (4,6,5,7)?arrow_forwardHow can you distinguish between 1,3-cyclohexadiene and 1,4-cyclohexadiene by oxidative cleavage reactionsarrow_forward
- Show that the [4 + 4] cycloaddition of two butadiene molecules to give cycloocta1,5-diene is thermally forbidden but photochemically allowedarrow_forward-Ocimene is a pleasant-smelling hydrocarbon found in the leaves of certain herbs. It has the molecular formula C10H16 and a UV absorption maximum at 232 nm. On hydrogenation with a palladium catalyst, 2,6-dimethyloctane is obtained. Ozonolysis of -ocimene, followed by treatment with zinc and acetic acid, produces the following four fragments: (a) How many double bonds does -ocimene have? (b) Is -ocimene conjugated or nonconjugated? (c) Propose a structure for -ocimene. (d) Write the reactions, showing starting material and products.arrow_forwardGive the structures of two different alkyl bromides both of which yield the indicated alkene as the exclusive product of E2 elimination.arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning