Chapter 5. Alkanes, its halogen- and oxygen-containing compounds

Alkyl halides. Halothane, ethyl chloride

1. Halothane (Fluothane) - Halothanum 2-Bromo-1,1,1-trifluoro- 2-chloroethane		2. Ethyl chloride - Aethylii chloridum Chloroethane
	Contains thymol (0.01%) as a stabilizer

Appearance. Halothane is a clear colorless liquid. Ethyl chloride is gas (at room temperature) or colorless liquid (in the liquefied state). Both compounds have specific odors and boiling points.

Identification

General methods

The definition of the covalently bonded halogen:

a) Beilstein test - ignition of substance on copper wire:

b) analysis of Cl and Br. The process is carried out by mineralization (conversion of halogen to halide ion by burning in a flask with O₂ or heating with NaHCO₃) followed by identification (using AgNO₃ or chloramine B):

c) analysis of F. The process is carried out with a zirconium-alizarin reagent or Fe(SCN)₃ after mineralization (by fusing with metallic Na):

Specific methods

Ethyl chloride

Flame test - green color.

Halothane

a) IR spectroscopy;

b) refractometry.

Assay

General method

Gas chromatography.

Specific method

Ethyl chloride

Back alkalimetry. Add an excess of NaOH (titrant 1) solution to the drug sample. Titrate an unreacted NaOH with HCl (titrant 2) until colorless solution is obtained (indicator - phenolphthalein). Carry out a blank titration.

Alcohols. Ethanol, glycerin

1. Ethyl alcohol 96%, 95%, 90%, 70%, 40% (Ethanol) - Spiritus aethylicus (Ethanolum) Ethanol	2. Glycerol (Glycerin) - Glycerolum (Glycerinum) Propane-1,2,3-triol
С2H5OH

Appearance. Ethanol is clear colorless liquid with characteristic odor. Glycerol is clear colorless odorless viscous liquid. Both compounds have specific densities and boiling points.

Acid-base properties. Ethanol reacts only with alkali metals (Na, K) while glycerol reacts with alkalis (NaOH, KOH) and forms the corresponding alcoholates.

Identification

Specific methods

Ethanol

Ethyl acetate and iodoform formation:

Glycerol

a) IR spectroscopy;

b) acrolein and copper glycerate formation:

Impermissible impurities in ethanol: methanol, aldehydes, esters, fusel oil (or fusel alcohol, or fuselol; determined by gas chromatography), furfural (determined by a negative reaction with aniline in the presence of acetic acid).

Assay

Specific methods

Ethanol

Gas chromatography.

Glycerol

Indirect alkalimetry. The drug is oxidized to formic acid by NaIO₄ and H₂SO₄, then the unreacted NaIO₄ is removed using ethylene glycol. The resulting formic acid is titrated with HCl to pink solution (indicator - phenolphtalein). Carry out a blank titration.

Ethers and esters. Diethyl ether, anaesthetic ether, nitroglycerin

1. Diethyl ether - Aether diaethylicus (Aether medicinalis) 1,1’-oxydiethane	3. Nitroglycerin, 1% solution in alcohol (nitroglycerin, glyceryl trinitrate) - Nitroglycerini solution spirituosa 1% (Nitroglycerinum) Propane-1,2,3-triyl trinitrate
2. Anaesthetic ether - Aether anaesteticus (Aether pro narcosi)
1,1’-oxydiethane Contains p-phenylenediamine as antioxidant

Appearance. Diethyl ether and anaesthetic ether are clear colorless volatile liquids with specific odor. Nitroglycerin solution is a clear colorless liquid with a certain density.

Impermissible impurities in diethyl ether: organic peroxides (determined by the negative reaction with aniline in the presence of acetic acid).

Identification

General methods:

a) relative density (diethyl ether, anaesthetic ether, nitroglycerin);

b) boiling point (diethyl ether, anaesthetic ether).

Specific methods

Nitroglycerin:

a) IR spectroscopy;

b) thin layer chromatography (TLC);

c) formation of benzidine (reaction on NO₂ group):

Assay

Specific method

Nitroglycerin^

Spectrophotometry in the visible region (λ = 410 nm) after acid hydrolysis and preparation of a color salt with phenoldisulfonic acid:

Aldehydes and their derivatives. Formaldehyde, chloral hydrate, methenamine

1. Formaldehyde solution (Formaldehyde) - Formaldehydi solutio (Formaldehyde) Formaldehyde		3. Methenamine (Hexamethylenetetramine, hexamine, or urotropin) - Methenaminum (Hexamethylentetraminum) 1,3,5,7- tetraazaadamantane
	Contains methanol as stabilizer
2. Chloral hydrate - Chloralum hydratum 2,2,2-trichloroethane-1,1-diol

Appearance. Formaldehyde is a clear colorless liquid with specific pungent odor. Chloral hydrate - colorless transparent hygroscopic crystals with pungent odor, slowly evaporate in air. Methenamine - colorless transparent odorless crystals, sublimate when heated.