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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.
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Reaction diethyl ether with concentrated HBr

Problem: When diethyl ether (CH 3 CH 2 OCH 2 CH 3 ) is treated with concentrated HBr, the initial products are CH 3 CH 2 Br and CH 3 CH 2 OH. Propose a mechanism (show electron movement using arrows) to account for this reaction. Solution: The mechanism includes two steps : protonation and SN 2 reaction:
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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.
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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. 
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How many molecules of substances B are produced when 29.3 g of substance A reacts? The molar mass of substance A is 23.5 g/mol?

 Task: How many molecules of substances B are produced when 29.3 g of substance A reacts? The molar mass of substance A is 23.5 g/mol? Solution:   There is a reaction A →B, one molecule A produce one molecule B.  We can determine the number of the molecules: when N – number of molecules, Na – Avogadro constant, n – amount of substance, m – mass of substance, M – molar mass of substance.   (molecules). Answer: 7.5∙10 23 molecules of substances B.
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