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:

C₄H₁₀	HDI =0.5x(2x4 + 2 + 0 – 10 – 0) = 0
C₄H₈	HDI = 0.5x(2x4 + 2 + 0 – 8 – 0) = 1
C₄H₆	HDI = 0.5x(2x4 + 2 + 0 – 6 – 0) = 2
C₄H₄	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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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.

Why is organic chemistry so important in the study of biology? Organic chemistry is a science about organic compounds , their properties and reactions and biology studies living organisms. All of them comprised of water, minerals and organic compounds . It is impossible to understand how works a living organism without understanding chemical processes inside. DNA, RNA, enzymes, amino acids, carbohydrates all are organic compounds that have physical and chemical properties that studies by organic chemistry.

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