(a)
Interpretation: The stereochemistry of given reaction is to be predicted.
Concept introduction: Cycloaddition reactions are pericyclic reactions that take place in two compounds containing pi bonds to form a cyclic compound. These reactions are concerted and stereospecific in nature. According to Woodward-Hoffmann rules, the polyene containing even number of bonds in thermal conditions undergoes reaction in antrafacial fashion and polyene containing odd number of bonds undergo reaction in suprafacial fashion. The total number of bonds present in the
(b)
Interpretation: The stereochemistry of given reaction is to be predicted.
Concept introduction: Electrocyclic reactions involve ring opening or ring closure in a conjugated polyene. According to Woodward-Hoffmann rules, the polyene containing even number of bonds in photochemical conditions undergoes reaction in disrotatory fashion and polyene containing odd number of bonds undergo reaction in conrotatory fashion.
(c)
Interpretation: The stereochemistry of given reaction is to be predicted.
Concept introduction: Cycloaddition reactions are pericyclic reactions that take place in two compounds containing pi bonds to form a cyclic compound. These reactions are concerted and stereospecific in nature. According to Woodward-Hoffmann rules, the polyene containing even number of bonds in photochemical conditions undergoes reaction in suprafacial fashion and polyene containing odd number of bonds undergo reaction in antrafacial fashion. The total number of bonds present in the alkenes is considered.
(d)
Interpretation: The stereochemistry of given reaction is to be predicted.
Concept introduction: Sigmatropic rearrangements are pericyclic reactions which takes place by concerted mechanism. In these rearrangements migration of sigma bond takes place. According to Woodward-Hoffmann rules, the total number of electron pairs in sigma bond that is broken and the pi bonds that rearrange. The polyene containing even number of electron pairs and bonds in thermal conditions undergoes reaction in antrafacial fashion and polyene containing odd number of electron pairs and bonds undergo reaction in suprafacial fashion.
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Chapter 27 Solutions
ORGANIC CHEMISTRY
- a. Show that [4+4] cycloaddition of two butadiene molecules to give cycloocta-1,5-diene is thermally forbidden but photochemically allowed b.Thermally allowed cycloaddition of the two butadiene molecules when there's a different. Show reaction and explain why it is thermally allowarrow_forwardB. Describe the stereochemistry (with structures) of the addition of Br2 and H₂O to cyclohexene. C. Arrange the following ions by increasing basicity, where 1 is the most basic and 5 is the least. HCEC CH3CH3NH2 CH3CH₂O CH3CH₂ H₂C=CHarrow_forwardPredict the products of the reactions. Show stereochemistry, using wedges and dashes, in the products and draw both enantimers.arrow_forward
- h. 3-methyl-1-butene with Hg(OAC)2 and CH3OH, followed later by NaBH4 CH3 H2C=CH-CH-CH3 Major Product(s) of h. Stereochemistry of the product described in h. (Circle one) а. R b. S С. Е d. Z e. a mixture of E and Z f. erythro g. threo h. a racemic (50/50) mixture i. all 4 products (a set of erythro and a set of threo) j. no stereochemistryarrow_forwardDraw the products of each Diels–Alder reaction, and indicate the stereochemistry.arrow_forwardDraw the structure of the major organic product of the reaction below. CH3CH2 CH2CH3 Zn(Cu) C=C CH212 ether H H • Use the wedge/hash bond tools to indicate stereochemistry where it exists. • Show stereochemistry in a meso compound. • If the reaction produces a racemic mixture, just draw one stereoisomer. opy aste ChemDoodlearrow_forward
- Determine the double bond stereochemistry (E or Z) for the following molecules. F. H3C C A CH3 F. H B D Brarrow_forwardDraw the products of the following Diels–Alder reactions. Indicate stereochemistry where appropriate and show the pushing mechanism for a and barrow_forwardWhy does a [2+2] cycloaddition reaction require a thermal condition to be met for initiation?arrow_forward
