Concept explainers
(a)
Interpretation: The product formed by the thermal electrocyclic ring closure of given triene N is to be determined.
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 product formed by the photochemical electrocyclic ring closure of given triene N is to be determined.
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.
(c)
Interpretation: The given processes are to be labeled as conrotatory or disrotatory.
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. In Conratotory process, the orbitals where rearrangement is taking place rotates in clockwise direction and in disrotatory process the atomic orbitals rotates in opposite direction.
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ORGANIC CHEMISTRY
- Consider the tetracyclic compound with rings labeled A–D. (a) Which ring is the most reactive in electrophilic aromatic substitution? (b) Which ring is the least reactive in electrophilic aromatic substitution?arrow_forwardThe endiandric acids comprise a group of unsaturated carboxylic acids isolated from a tree that grows in the rain forests of eastern Australia. The methyl esters of endiandric acids D and E have been prepared from polyene Y by a series of two successive electrocyclic reactions: thermal ring closure of the conjugated tetraene followed by ring closure of the resultingconjugated triene. (a) Draw the structures (including stereochemistry) of the methyl esters of endiandric acids D and E. (b) The methyl ester of endiandric acid E undergoes an intramolecular [4 + 2] cycloaddition to form the methyl ester of endiandric acid A. Propose a possible structure for endiandric acid A.arrow_forward(a) What product is formed when each compound undergoes a thermal electrocyclic ring opening? (b) What product is formed when each compound undergoes a photochemical electrocyclic ring opening?arrow_forward
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- For alkenes A, B, C, and D: (a) Rank A—D in order of increasing heat of hydrogenation; (b) rank A—D in order of increasing rate of reaction with H2, Pd-C; (c) draw the products formed when each alkene is treated with ozone, followed by Zn, H2O.arrow_forward(a) Explain how pyrrole is isoelectronic with the cyclopentadienyl anion.(b) Specifically, what is the difference between the cyclopentadienyl anion and pyrrole?(c) Draw resonance forms to show the charge distribution on the pyrrole structure.arrow_forwardCompound A exhibits a peak in its 1H NMR spectrum at 7.6 ppm, indicating that it is aromatic. (a) How are the carbon atoms of the triple bonds hybridized? (b) In what type of orbitals are the π electrons of the triple bonds contained? (c) How many π electrons are delocalized around the ring in A?arrow_forward
- Rank the compounds in each group according to their reactivity toward electrophilic substitution: (a) Chlorobenzene, o-dichlorobenzene, benzene (b) p-Bromonitrobenzene, nitrobenzene, phenol (c) Fluorobenzene, benzaldehyde, o-dimethylbenzenearrow_forward1.What is the product of the reaction between 1,3-dibutene and bromoethene? (A) No reaction occurs (B) 4-bromocyclohexene (C) 3-bromocyclohexene (D) 3-bromocyclopentene 2. Cyclohexene undergoes hydrobromination. Which of these is a possible product? (A) Bromocyclohexane (B) All of these (C) Trans 1,2-dibromocyclohexane (D) Cis 1,2-dibromocyclohexane 3. A hydrocarbon molecule is saturated if the molecule contains (A) Single covalent bonds, only (B) A double covalent bond, only (C) A triple covalent bond (D) Single and double covalent bondsarrow_forward(a) What is the major alkene formed when A is dehydrated with H2SO4? (b) What is the major alkene formed when A is treated with POCl3 and pyridine? Explain why the major product is different in these reactions.arrow_forward
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