Concept explainers
(a)
Interpretation: The given reaction is to be classified as electrocyclic reaction, cycloaddition, or sigmatropic rearrangement. The stereochemistry whether the given reaction is conrotatory, disrotatory, suprafacial, or antarafacial is to be indicated.
Concept introduction: Electrocyclic reactions are pericyclic reactions which takes place by concerted mechanism. These reactions involve ring opening or ring closure in a conjugated polyene
(b)
Interpretation: The given reaction is to be classified as electrocyclic reaction, cycloaddition, or sigmatropic rearrangement. The stereochemistry whether the given reaction is conrotatory, disrotatory, suprafacial, or antarafacial is to be indicated.
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 in thermal conditions undergoes reaction in antrafacial fashion and polyene containing odd number of bonds undergo reaction in suprafacial fashion.
(c)
Interpretation: The given reaction is to be classified as electrocyclic reaction, cycloaddition, or sigmatropic rearrangement. The stereochemistry whether the given reaction is conrotatory, disrotatory, suprafacial, or antarafacial is to be indicated.
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.
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Chapter 27 Solutions
Organic Chemistry
- Intramolecular Diels–Alder reactions are possible when a substrate contains both a 1,3-diene and a dienophile, as shown in the following general reaction.With this in mind, draw the product when each compound undergoes an intramolecular Diels–Alder reaction.arrow_forwardConsider this scheme. Why does a ring form with a single ethylene glycol on A rather than two molecules of ethylene glycol to form acyclic acetals? Intramolecular reactions are A unfavorable when compared to intermolecular reactions Acyclic molecules are unfavorable compared to rings В in all cases The change in entropy is favorable for ring formation and strain is low in a five- membered ring Sterics prevents acyclic molecules from forming in this D case H HCI + HOCH2CH2OH H + H2Oarrow_forwardG.289.arrow_forward
- Ll.113.arrow_forwardFor each reaction below, provide all the expected constitutional isomer monohalogenated products. Ignore stereochemistry and do not include duplicates of the same constitutional isomers. Consider the expected selectivity (or lack of) for the chlorination and bromination reactions. Also consider possible resonance structures where appropriate a. b. Cl₂ heat NBS lightarrow_forwardLl.44.arrow_forward
- Pertanyaan pada gambararrow_forwardIdentify compounds A – E of the reaction sequence shown in Scheme III, making sure to include stereochemistry as appropriate.a) Identify compound A in Scheme III. b) Identify compound B in Scheme III. c) Identify compound C in Scheme III. d) Identify compound D in Scheme III. e) Identify compound E in Scheme III.arrow_forwardThe bicyclic alkene P can be prepared by thermal electrocyclic ringclosure from cyclodecadiene Q or by photochemical electrocyclic ringclosure from cyclodecadiene R. Draw the structures of Q and R, andindicate the stereochemistry of the process by which each reactionoccurs.arrow_forward
- Items 49-51: Given the following reaction: CH3 H. CH3 49. What is the product of the reaction? A. В. C. D. 50. Which MO will be involved in this electrocyclic reaction? 888888 888888 888888 A. B. C. 51. The reaction will go through: A. a conrotatory motion B. a disrotatory motion C. none of thesearrow_forwardHow many products are obtained following a monochlorination reaction (Cl2, UV) if the stereochemistry is not taken into consideration?arrow_forwardConsider the following nucleophilc substitution. LOCH3 Br OCH3 в A a. Identify the reaction conditions A and specify the reaction mechanism for the nucleophilic substitution. Explain your choice. b. Explain why the transformation does not give rise to significant elimination. c. Which product(s) B is formed in the reaction? Please specify the stereochemistry clearly with reference to the reaction mechanism.arrow_forward
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