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
- What product is formed when each compound undergoes thermal electrocyclic ring opening or ring closure? Label each process as conrotatory or disrotatory and clearly indicate the stereochemistry around tetrahedral stereogenic centers and double bonds. а. b.arrow_forward6 of 21 4. Sigmatropic Rearrangements For each reaction: symmetry Indicate which п molecular orbital is the HOMO and its Determine if the rearrangement would be suprafacial or antarafacial Draw an arrow pushing mechanism Draw the structure of the major product Describe the rearrangement e.g. [3,3] type type type type hv hy 6 closure closure closure closurearrow_forwardDevise a stepwise synthesis of each compound from dicyclopentadiene using a Diels–Alder reaction as one step. You may also use organic compounds having ≤ 4 C's, and any required organic or inorganic reagents.arrow_forward
- Ll.39.arrow_forwardProblem 13.28 What reagent is needed to convert (CH3)2CHCH₂ COCI to each compound? a. b. C. d. но Ho ГОНarrow_forwardDraw the major products obtained from the reaction of one equivalent of HBr with the following compounds. For each reaction, indicate the kinetic product and the thermodynamic productarrow_forward
- Ll.105.arrow_forwardLl.112.arrow_forwardIntramolecular 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_forward
- Provide the reagents. Но + enantiomer A 1. KOt-Bu, heat 2. mCPBA 3. MeMgBr 4. H2O B. 1. conc. H,SO4, heat 2. MCPBA 3. MeBr С. 1. РBгз 2. KOt-Bu 3. mCPBA 4. MeMgBr 5. H2O D. 1. Br2, hv 2. KOt-Bu 3. mCPBA 4. MeMgBr 5. H2O E. 1. Br2, hv 2. KOt-Bu 3. MCPBA 4. MeBr 5. H2O F. 1. Br2, FeBr3 2. KOt-Bu 3. mCPBA 4. MeMgBr 5. H2O G. 1. Br2, FeBr3 2. KOt-Bu 3. mCPBA 4. MeBr 5. H20arrow_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_forwardDraw all stereoisomers formed in each reaction.arrow_forward
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