Question. Give the structures of intermediates A through H in the following synthesis of trans-1-cyclohexyl-2-methoxycyclohexane.

Short Answer

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Cyclohexanol on reaction with sulphuric acid followed by heating undergoes dehydration, and forms alkene which is product A. Product A undergoes epoxidation and forms product F which on reaction with product E undergoes coupling, and forms product G. Product A on alkoxymercuration-demercuration leads to the formation of product B in which methoxy group is attached.

Product B on reaction with hydrogen bromide followed by heating undergoes elimination and methoxy group acts as a good leaving group, and bromide ion adds to the alkene carbon which forms bromocyclohexane which is product D. Side product formed is methylbromide which is product C.

Formation of products A, B, C, D, E, F and G

Step by step solution

01

Step-1. Formation of products A, B, C, D, E, F, G:

Cyclohexanol on reaction with sulphuric acid followed by heating undergoes dehydration, and forms alkene which is product A. Product A undergoes epoxidation and forms product F which on reaction with product E undergoes coupling, and forms product G. Product A on alkoxymercuration-demercuration leads to the formation of product B in which methoxy group is attached.

Product B on reaction with hydrogen bromide followed by heating undergoes elimination and methoxy group acts as a good leaving group, and bromide ion adds to the alkene carbon which forms bromocyclohexane which is product D. Side product formed is methylbromide which is product C.

Formation of products A, B, C, D, E, F and G

02

Step-2. Formation of product H:

Product G undergoes reduction reaction with sodium and forms product H in which oxygen of hydroxyl group has negative charge and acts as a good nucleophile and further on reaction with methylbromide, the oxygen anion attacks at methyl and substitution reaction takes place which forms final product.

Formation of product H

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Most popular questions from this chapter

One of the crowning achievements of natural products synthesis was Bryostatin 1, published by Professor Gary Keck (University of Utah; Journal of the American Chemical Society,2011, 133, 744-747). The Bryostatins are a family of compounds isolated from aquatic invertebrates known as Bryozoans. The compounds are of interest for a variety of biological effects, including anti-cancer activity and reversing brain damage in rodents.

a. How many ether functional groups are present in Bryostatin 1?

b. Identify the other oxygen-containing functional groups.

c. This is called a macrolide because it contains a large number of atoms in the large ring. How many atoms are in the large ring?

d. How many chiral centers are in this molecule?

e. Using the number of chiral centers you reported in part (d), calculate the number of stereoisomers possible at these chiral centers. (Ignore stereoisomers at double bonds.)

1,4-Dioxane is made commercially by the acid-catalyzed condensation of an alcohol.

(a)Show what alcohol will undergo condensation, with loss of water, to give 1,4-dioxane.

(b)Propose a mechanism for this reaction

Show how the following ethers might be synthesized using (1) alkoxymercuration-demercuration and (2) the Williamson synthesis. (When one of these methods cannot be used for the given ether, point out why it will not work.)

  1. 2-methoxybutane
  2. Ethyl cyclohexyl ether
  3. 1-methoxy-2-methylcyclopentane
  4. 1-methoxy-1-methylcyclopentane
  5. 1-isopropoxy-1-methylcyclopentane
  6. Tert-butyl phenyl ether

Question. Glycerol (propane-1,2,3-triol) is a viscous syrup with molecular weight 92g/mol, boiling point 290oC, and density 1.24g/mol. Transforming the three hydroxy groups into their trimethylsilyl ethers (using chlorotrimethylsilane and a tertiary amine) produces a liquid that flows easily, has molecular weight 309g/mol, boiling point approximately 180oC, and density 0.88g/mol. Draw the structures of these two compounds and explain why glycerol has a lower molecular weight but a much higher boiling point and density.

Question: (a) Predict the values of m/zand the structures of the most abundant fragments you would observe in the mass spectrum of di-n-propyl-ether.

(b) Give logical fragmentations to account for the following ions observed in the mass spectrum of 2-methoxypentane: 102,87,71,59,31.

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