Difference between revisions of "Methanol"

Revision as of 16:47, 31 December 2018

Methanol

Methanol sample and its original bottle.
Structure of methanol
Names
IUPAC name Methanol
Systematic IUPAC name Methanol
Other names Carbinol, Columbian spirits, Hydroxymethane, Methyl alcohol, Methyl hydrate, Methyl hydroxide, Methylic alcohol, Methylol, Pyroligneous spirit, Wood alcohol, Wood naphtha, Wood spirit
Identifiers
Jmol-3D images	Image
SMILES CO
Properties
Chemical formula	CH4O CH3OH
Molar mass	32.04 g/mol
Appearance	Colorless volatile liquid
Odor	Alcoholic
Density	0.810 g/cm3 (0 °C) 0.792 g/cm3 (20 °C) 0.7866 g/cm3 (25 °C)
Melting point	−97.6 °C (−143.7 °F; 175.6 K)
Boiling point	64.7 °C (148.5 °F; 337.8 K)
Solubility in water	Miscible
Solubility	Reacts with acetyl chloride, formic acid, thionyl chloride Miscible with benzene, diethyl ether, ethanol, glycerol, pentane, pyridine, toluene, xylene
Vapor pressure	13.02 kPa (at 20 °C)
Acidity (pKa)	15.5
Hazards
Safety data sheet	ScienceLab
Flash point	11 to 12 °C
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	5628 mg/kg (rat, oral) 7300 mg/kg (mouse, oral) 12880 mg/kg (rat, oral) 14200 mg/kg (rabbit, oral)
LC50 (Median concentration)	64,000 ppm (rat, 4 hr)
Related compounds
Related compounds	Ethanol Propanol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Methanol, or methyl alcohol is the simplest alcohol, with the formula CH₃OH, also abbreviated as MeOH. It is a light, colorless, volatile, flammable liquid. It is an important chemical as a solvent and feedstock organic compound.^[1]

Properties

Chemical

Methanol is a starting point for many organic compounds, such as formaldehyde, which is produced by oxidation of methanol.

CH₃OH + [O] → CH₂O + H₂O

Methanol burns when ignited in air to give carbon dioxide and water vapors. Minute traces of formaldehyde are produced as side product if there isn't an excess of oxygen during burning.

2 CH₃OH + 3 O₂ → 2 CO₂ + 4 H₂O

Reaction of methanol with a haloacid, such as hydroiodic acid will give methyl iodide.

CH₃OH + HI → CH₃I + H₂O

Unlike ethanol, the addition of hypochlorite anion to methanol will not give chloroform, but rather methyl hypochlorite, a very dangerous and unstable compound that decomposes violently and can even explode at high concentrations.

CH₃OH + 2 NaClO → CH₃ClO + NaCl + NaOH

Methanol vapors in air will decompose over the course of several days to form carbon dioxide and water vapor.^[2] Methanol is used in the production of biodiesel.

Physical

Methanol is a colorless, volatile, flammable liquid, with an alcoholic odor. It has a molecular weight of 32.04, a boiling point of 65°C and a density of 0.7914 g/cm³.^[3] Methanol is miscible with a variety of organic and inorganic solvents, though not as many as ethanol. Methanol/water mixtures can be separated into two layers by salting-out with potassium carbonate.

Availability

A type of antifreeze and automotive cleaner known as Heet can be found in most gas stations in the United States and is 99% or higher methanol. Some alternative fuels are entirely or mostly made of methanol, and due to the large quantities typically sold this can be a very efficient way to purchase it.

Methanol is sometimes sold at paint supply stores as wood alcohol, or methyl alcohol.^[4] It can also be bought from scientific suppliers in higher grades. Hardware supplies sometimes sell methanol as "methyl hydrate" or "methylated spirits". Finally, some home fireplaces use methanol as fuel, so it can be found in this manner as well. Some window cleaning solutions contain 50-90% methanol, along with traces of water and dye, as well traces of ethanol and or isopropanol.

In some countries the sale of "clean" (high purity) methanol may be regulated, being classified poison or due to its use in counterfeit alcohol. Since May 2018, the sale of window washers containing more than 0.6% methanol is restricted in the EU countries, though the ban seems to be largely ignored in many places.^[5]

Preparation

Impure methanol can be obtained via destructive distillation of wood. The process is not economically viable on a small scale, and produces many side products/contaminants, acetic acid, acetone, and tars among them. It is still an interesting process though, and could be attempted solely for educational value.^[6]

Another possible preparation route involves the hydrolysis of methyl esters, like methyl benzoate.^[7]

Projects

• Make formaldehyde
• Make trimethyl borate
• Make methyl salicylate and other methyl esters
• Methyl iodide synthesis
• Dimethyl ether synthesis
• Direct methanol fuel cell

Handling

Safety

Methanol is significantly more toxic than other common alcohols such as ethanol or isopropanol, as it is metabolized to formic acid in the body, causing blindness and death at high doses.

Methanol flames tend to have extremely low visibility, particularly in the daytime or well-lit environments, making burning methanol difficult to detect and posing a great risk. If it is being used in instances where burning is likely, the addition of a small amount of boric acid colors the flame green and allows it to be seen.

One of the most insidious traits of methanol is that is is hard to distinguish from ethanol, they have a similar appearance, smell and taste. Accidentally consuming methanol may be lethal. In case if methanol is accidentally consumed, the first aid is giving the patient ethanol, orally, preferably in the form of vodka, until the state of "absolutely shit-faced", and then immediately calling the ambulance. Ethanol does not neutralize the effect of methanol but competes with it and prevents its immediate metabolism, giving the doctors more time to save the patient. If no medical attention is available, the only cure is continuously giving the patient ethanol until all methanol is purged from his organism unmetabolized. As a rule of thumb, three days of binge drinking forced upon the patient is enough to completely thwart methanol poisoning.

One urban, though not very accurate, way to detect methanol involves inserting a red-hot piece of copper wire into the alcohol. If vapors have a stinging smell like "morgue" or "dissected frogs" (the odor of formaldehyde), then the alcohol contains methanol, though this method is not very reliable, and is only effective at high concentrations.

Storage

Methanol is best kept in glass bottles in dark places. Methanol should be kept out of rooms with an open flame, as it is highly volatile and flammable. Methanol bottles should be clearly marked with the name of the compound, the "skull and crossbones" sign and a clarifying addendum "This is not ethanol, you moron!", especially in houses where drinkable ethanol is also kept.

Disposal

Burning methanol is a good way to destroy it. Do this outside or in a fume hood. Since methanol burns with an almost invisible flame, which can be a serious risk, it is a good idea to make the flame visible by mixing the methanol with another solvent, like ethanol or acetone. Try not to burn too much at once, to prevent its vaporization in the air or inhalation of partial oxidation products such as formaldehyde, formic acid, or carbon monoxide.

References

1. ↑ http://en.wikipedia.org/wiki/Methanol
2. ↑ http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=887&loc=ec_rcs#itabs-2d
3. ↑ CRC Handbook of Chemistry and Physics 66th Edition, 1985
4. ↑ http://en.wikipedia.org/wiki/List_of_commonly_available_chemicals#L.E2.80.93N
5. ↑ https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:32018R0589
6. ↑ http://www.sciencemadness.org/talk/viewthread.php?tid=2652
7. ↑ https://www.youtube.com/watch?v=GJMGzIQE4RM

Relevant Sciencemadness threads

• Methanol -> methanal(formaldehyde)
• Destructive Distillation of Wood
• Methanol Synthesis(Newer thread)