Foul-Smelling Components

Several species with foul odors cause problems in wood industries, such as lumber sawing and the manufacture of plywood and laminated wood. A few species contain these components in fresh wood - for example, pyridine and 3-methylpyrro-lidine in elima wood (Octomeles sumatrana) and sulfides in Bawang hutan (Scor-docarpus borneensis) (35). 

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A drawback to the nse of methane and ethane is that they cannot be economically transported in a gas cylinder. Two other gases, propane and butane, are suitable for this sort of transportation. Their mixture is called LPG gas (liquefied petroleum gas), and it is extensively nsed in remote or underdeveloped locations where gas cannot be obtained from the pipehnes. The main components of LPG are odorless as well, and foul-smelling additives are used in the cylinders for safety. 

Butyric acid, for instance, has a strong odor like that of rancid buffer (of which if is an ingredient) and is a component of what we normally call body odor. It is this substance that makes foul-smelling humans so easy for an animal to defecf when downwind of them. It is also of great help to the bloodhound, which is trained to follow small fraces of this odor. 

The lower-molecular-weight thiols and sulfides are most notorious for their foul smell. Ethanethiol is detectable by its odor even when it is diluted in 50 million parts of air. The major volatile components of the skunk s defensive spray are 3-methyl-1-butanethiol, trans-2-butene-l-thiol, and tra i-2-butenyl methyl disulfide. The all-too-familiar human BO (body odor) emanating from sweaty armpits was analyzed by chemists in the perfume industry in 2004. The major chemical culprit is 3-mercapto-3-methylhexan-l-ol, specifically the obnoxious 5-enantiomer. It is excreted admixed with 25% of its mirror image, which, curiously, has a fruity odor. 

One other physical property of carboxylic acids must be mentioned The liquid carboxylic acids, from propanoic acid to decanoic acid, have extremely foul odors, about as bad as those of thiols, though different. Butanoic acid is found in stale perspiration and is a major component of locker room odor. Pentanoic acid smells even worse, and goats, which secrete Ce, Cg, and Qo acids, are not famous for their pleasant odors. 

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