Reaction diethyl ether with concentrated HBr

Problem:

When diethyl ether (CH₃CH₂OCH₂CH₃) is treated with concentrated HBr, the initial products are CH₃CH₂Br and CH₃CH₂OH. Propose a mechanism (show electron movement using arrows) to account for this reaction.

Solution:

The mechanism includes two steps: protonation and SN₂ reaction:

Comments

Index of Hydrogen Deficiency (IHD)

Alkanes are saturated organic compounds with number of hydrogens 2n + 2 (n is number of carbons). All organic compounds that have less hydrogens than 2n+2 have a degree of unsaturation: The hydrogen deficiency index (HDI) or Index of hydrigen deficiency (IDH) is a measure of the number of degrees of unsaturation. A compound has one degree of unsaturation for every two hydrogen atoms that are missing. There is a formula to determine IDH: IDH = 0.5x(2C + 2 + N − H − X ) C is number of carbons N is number of nitrogens X is number of halogens For compounds mentioned above: C 4 H 10 HDI = 0.5x(2x4 + 2 + 0 – 10 – 0) = 0 C 4 H 8 HDI = 0.5x(2x4 + 2 + 0 – 8 – 0) = 1 C 4 H 6 HDI = 0.5x(2x4 + 2 + 0 – 6 – 0) = 2 C 4 H 4 HDI = 0.5x(2x4 + 2 + 0 – 4 – 0) = 3 Please pay attention that we can determine IDH as well from brutto formula as from structure.

Problem: The value of K (@25 o C) for compound A when partitioned between water and cycloheptane is 3.37. Starting with a solution of 848 g of compound A in 497 mL of water what quantity of compound A (in grams) would remain in the water layer after two successive extractions with cycloheptane each using 331 mL of cycloheptane. Solution: The issue can be easily solved using two simple steps: 1. We should find the recovery factor for two successive extractions: 2. Finding the mass of compound A that remains in water: Answer: 80.1 g of compound A would remain in the water.

Determine the specific rotation of epinephrine

Problem: A solution of 0.50 g of (-)-epinephrine dissolved in 10.0 mL of dilute aqueous HCl was placed in a 20-cm polarimeter tube. Using the sodium D line, the rotation was found to be -5.1° at 25 °C. Determine the specific rotation of epinephrine. Solution: Specific rotation can be determined with a formula: Where a is an observed rotation (degrees), c is a concentration (g/mL) and l is the length of the tube (dm). T = 25°C λ=D, that means a sodium line (589 nm) Answer: specific rotation of epinephrine is – 51.

OCHEMOS

Search This Blog