Interpretation:
Thermal electrocyclic ring closure of (2Z, 4Z, 6Z)-2,4,6-octatriene yielding products via conrotatory and disrotatory cyclizations.
Concept introduction:
Conrotatory and disrotatory is based on the rotation at each end of the molecule. In conrotatory mode, both atomic orbitals of the end groups turn in the same direction ,such as both atomic orbitals rotating clockwise or counter-clockwise. In disrotatory mode, the atomic orbitals of the end groups turn in opposite directions ,one atomic orbital turns clockwise and the other counter-clockwise. The cis/trans geometry of the final product is directly decided by the difference between conrotation and disrotation.
Whether a particular reaction is conrotatory or disrotatory can be accomplished by examining the molecular orbitals of each molecule and through a set of rules. Only two pieces of information are required to determine conrotation or disrotation using the set of rules: how many electrons are in the pi-system and whether the reaction is induced by heat or by light. This set of rules can also be derived from an analysis of the molecular orbitals for predicting the stereochemistry of electrocyclic reactions.
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Chapter 30 Solutions
Organic Chemistry
- (2R,3S)-2-Bromo-3-phenylbutane undergoes an E2 elimination when treated with sodium methoxide. Draw all possible Newman projections for the bond relevant for the elimination reaction, and use those Newman projections to explain the stereochemical outcome of the reaction. Draw the final product and provide its IUPAC name.arrow_forwardWhen 3,3-dimethyl-1-butene is treated with HBr alone, the major product is 2-bromo-2,3-dimethylbutane. When the same alkene is treated with HBr and peroxide, the sole product is 1-bromo-3,3-dimethylbutane. Explain these results by referring to the mechanisms.arrow_forwardWhich of the following best describes the stereochemistry of ring closure and the product for the following reaction? (3E,5Z,7E)-3,5,7-decatriene hv A) disrotatory, cis-5,6-diethyl-1,3-cyclohexadiene B conrotatory, cis-5,6-diethyl-1,3-cyclohexadiene disrotatory, trans-5,6-diethyl-1,3-cyclohexadiene conrotatory, trans -5,6-diethyl-1,3-cyclohexadienearrow_forward
- When 3-bromo-1-methylcyclohexene undergoes solvolysis in hot ethanol, two productsare formed. Propose a mechanism that accounts for both of these productsarrow_forwardThere are two stereoisomers of 1-tert-butyl-4-chloro-cyclohexane. One of these isomers reacts with sodium ethoxide in an E2 reaction that is 500 times faster than the reaction of the other isomer. Identify the isomer that reacts faster and explain the difference in rate for these two isomers.arrow_forwardConsider the following chemical transformation:The transformation takes place via two sequential pericyclic reactions. Identify the two reactions and give a critical explanation whether the reactions are allowable or not. Explain the stereochemistryarrow_forward
- When 3,3-dimethylbut-1-ene is treated with HBr alone, the major product is 2-bromo-2,3- dimethylbutane. When the same alkene is treated with HBr and peroxide, the sole product is 1-bromo-3,3-dimethylbutane. Explain these results by referring to the mechanisms.arrow_forwardWhat is the expected major product of reacting cyclohexane carbaldehyde with (CH3)2NH?arrow_forwardTreatment of the following stereoisomer of 1-bromo-1,2-diphenylpropane with sodium ethoxide in ethanol gives a single stereoisomer of 1,2-diphenylpropene. I H C6H5 H3C Br C6H5 CH3CH2O Na+ CH3CH2OH Draw the E2 elimination product of the reaction. Take into account that the starting stereochemistry affects the resulting double bond stereochemistry. • Consider E/Z stereochemistry of alkenes. • Do not show stereochemistry in other cases. •You do not have to explicitly draw H atoms. • In cases where there is more than one answer, just draw one.arrow_forward
- What are the reaction products of (R)-3-methylcyclohexene in the reaction sequence of hydroboration-oxidation: I- (1S,2R)-2-methylcyclohexanol + (1R,2R)-2-methylcyclohexanol, barely II- (1S,2R)-2-methylcyclohexanol + (1R,2S)-2-methylcyclohexanol, barely III- (1S,3R)-3-methylcyclohexanol + (1R,3R)-3-methylcyclohexanol, barely IV- (1S,3R)-3-methylcyclohexanol + (1S,3S)-3-methylcyclohexanol, barely V- Alternatives I and III contain the reaction products VI- ndaarrow_forwardIdentify the pericyclic reactions in the followingreaction schemes. Give the complete reaction name and indicate the course of the reaction with the aid of the arrow notation.arrow_forwardIf 2,4-dimethylcyclopentane-1-carbonyl chloride reacts with propan-2-ol. What product is obtained?arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning