Interpretation:
Whether the reaction shown will take place in conrotatory or disrotatory manner is to be stated. The stereochemistry of the cyclobutene product is to be given and explained.
Concept introduction:
An electrocyclic reaction involves the cyclization of a conjugated acyclic system. These reactions are reversible and are highly stereospecific.
In elecrocyclic reactions involving even number of electron pairs, a thermal reaction occurs in conrotatory manner and a photochemical reaction occurs in disrotatory manner.
In elecrocyclic reactions involving odd number of electron pairs, a thermal reaction occurs in disrotatory manner and a photochemical reaction occurs in conrotatory manner.
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Chapter 30 Solutions
Organic Chemistry
- Nonconjugated , -unsaturated ketones, such as 3-cyclohexenone, are in an acid-catalyzed equilibrium with their conjugated , -unsaturated isomers. Propose a mechanism for this isomerization.arrow_forwardShow how the following starting material is converted to the given product by a series of two pericyclic reactions. Account for the observed stereochemistry.arrow_forwardWhen 2-bromo-3-phenylbutane is treated with sodium methoxide, two alkenes result (by E2 elimination). The Zaitsevproduct predominates.(a) Draw the reaction, showing the major and minor products.(b) When one pure stereoisomer of 2-bromo-3-phenylbutane reacts, one pure stereoisomer of the major product results.For example, when (2R,3R)-2-bromo-3-phenylbutane reacts, the product is the stereoisomer with the methyl groups cis.Use your models to draw a Newman projection of the transition state to show why this stereospecificity is observed.(c) Use a Newman projection of the transition state to predict the major product of elimination of (2S,3R)-2-bromo-3-phenylbutanearrow_forward
- The reaction of (S)-2-bromopentane with potassium cyanide to yield 2-methylpentanenitrile (2-cyanopentane) occurs via a nucleophilic substitution pathway. The reaction is 100% stereospecific.arrow_forwardPredict the products of the following reactions. Be sure to indicate stereochemistry when necessary.arrow_forwardWhen 2-bromo-3-phenylbutane is treated with sodium methoxide, two alkenes result (by E2 elimination). The Zaitsevproduct predominates.(a) Draw the reaction, showing the major and minor products.(b) When one pure stereoisomer of 2-bromo-3-phenylbutane reacts, one pure stereoisomer of the major product results.For example, when (2R,3R)-2-bromo-3-phenylbutane reacts, the product is the stereoisomer with the methyl groups cis.Use your models to draw a Newman projection of the transition state to show why this stereospecificity is observedarrow_forward
- Predict the products of the following reactions. Show stereochemistry and regiochemistry of the product, where relevant.arrow_forwardPredict the product of the following reaction. Include stereochemistry if necessary.arrow_forwardIdentify the following pericyclic reaction; explain the course and stereochemistry of the reaction.arrow_forward
- Account for any stereochemistry, major/minor products in the following reactions. Provide mechanistic explanations for your product(s).arrow_forwardWhen treated with NaOH, the bromide below gives an alkene by the E2 mechanism, by elimination of the H atom indicated by the arrow: (a) Draw the Newman projection from which elimination takes place. (b) Draw the mechanism. (c) Draw the product with the proper stereochemistry. (d) Assign the proper stereochemical descriptor to the product. (e) Give the rate equationarrow_forwardIllustrate the resonance effect of the methoxy group -OCH3, on the structure of the benzene ring. Draw all the oissuvke resonance forms of methoxybenzene, including the hybrid Based on the structures, explain how the presence of the -OCH3 group affects: (i) the reactivity of the benzene ring towards electrophilic attack (ii) the orientation or point of attack of an incoming electrophilic reagent on the benzene ring.arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning