Molecules can have smell {odorant} to humans. Odorants must be volatile. Airborne-molecule chemical-bond configurations (shapes) and vibration and rotation frequencies and intensities cause smell. Odorant molecules have molecular weight greater than 35 and less than 350, not too small nor too large for olfactory receptors. Odorants are typically hydrophobic.
Pungent odorants are compact non-polar aryl compounds. Sweet odorants are non-polar chain esters. Sweaty odorants are polar chain organic acids. Right-handed and left-handed chiral molecules, like spearmint and caraway, smell different.
primary
People can distinguish 30 primary odorants:
alliaceous and garlicy: cysteine sulfur compounds
aromatic: benzene alkyls
asparagusy, bitter: carboxylic-acid thiols
biting, hanging, alcoholy: small alcohols
burnt, smoky: monophenols and polycyclic aromatic hydrocarbons
buttery: small aldehydes
camphorous, resinous: polycyclic aryls
cool and minty: cyclic alcohols
earthy, moldy, potatoey: cyclic ethers
fishy: alkyl and aryl monoamines
flowery, fresh: monoterpenoid alcohols
foul, rotten, sulfurous: small thiol sulfur compounds
fragrant, floral, flowery, ethereal: linear ethers
fruity, sweet: medium-chain alcohols and non-polar chain esters
goaty, hircine: medium-length polar chain carboxylic acids
grassy, herby: alkene aldehydes
malty: short-chain aldehydes
minty, spearminty, pepperminty: cyclic alkene ketones
musky, ambrosial: macrocyclic ketones
nutty, earthy, green peppery: heterocyclic aromatic amines
pharmaceutical, medicinal, pungent, unpleasant: halogens
pungent, acrid, vinegary: small carboxylic acids
putrid, sweaty, rancid: medium-short polar chain carboxylic acids
roasted, fermented, popcorny: heterocyclic aromatic amines
rubber: monoterpenes (isoprenes)
cabbage-like, rotten: methyl sulfides
savory, spicy: heterocyclic ketones
spermous: alkyl multi-amines and heterocyclic amines
tarry, oily: polyphenols
tobacco: alkenes-with-one-ring ketones
urinous: steroid ketones
woody: triterpenes (sesquiterpenes)
Odorants mix to make odor, and people can distinguish 10,000 different odors.
categories
Smells can range through sweet/flowery/fruity, mild/vegetably, mild/animaly, mild/mineraly, strong/vegetably, strong/animaly, putrid/animaly, and sharp/mineraly.
The smell-category sequence correlates with molecule reactivity:
Ether -C-O-C-
Alcohol -CH2OH
Ester -COO-
Aryl =CHC=
Terpene =CC2
Ketone -COC-
Aldehyde -CHO
Acid -COOH
Amine -CH2NH2
Sulfhydryl -CH2SH
Halogens Br2
similarities based on chemical group
Similar chemical types make similar smells. Similar chemical origins make similar smells.
Alcohols are similar: biting, fruity, sweet.
Aldehydes are similar: malty, grassy (herby).
Amines are similar: spermous, fishy, nutty, roasted.
Aryls are similar: aromatic, burnt (smoky), camphorous (resinous), tarry (oily).
Carboxylic acids are similar: pungent (acrid, vinegary), putrid (sweaty, rancid), goaty (hircine).
Ethers are similar: fragrant, floral, fruity and sweet.
Ketones are similar: minty, spicy, savory, tobacco, musky (ambrosial), urinous.
Sulfur compounds are similar: asparagusy, cabbage-like, alliaceous (garlicy), foul, rotten.
Terpenes are similar: minty, flowery (fresh), rubbery, woody.
similarities based on similar chemical groups
Alcohols and aryl ketones are similar: biting, fruity, minty, musky.
Alcohols and esters are similar: fruity, sweet.
Aldehydes and alkene ketones are similar: malty, grassy, tobacco.
Aldehydes and ethers are similar: malty, grassy, earthy.
Aldehydes and terpenes are similar: malty, grassy, rubbery, woody.
Amines and steroid ketones are similar: spermous, fishy, nutty, roasted, urinous.
Amines and carboxylic acids are similar: spermous, fishy, nutty, roasted, pungent, putrid, goaty.
Polycyclic aryls and halogens are similar: camphorous, pharmaceutical.
Carboxylic acids and steroid ketones are similar: pungent, putrid, goaty, urinous.
Alkene ketones and terpenes are similar: tobacco, rubbery, woody.
Polycyclic aryl ketones and ethers are similar: minty, camphorous, musky, fragrant, flowery, fruity.
similarities based on organism type
Vegetable smells are similar: alcohols, aldehydes, ethers, aryl and alkene ketones, sulfur compounds, terpenes.
Animal smells are similar: carboxylic acids, amines, polycyclic aryl ketones, steroid ketones.
opposites
Carboxylic acids (sour, putrid, animal) and esters (sweet, fruity, vegetable) are opposites.
Carboxylic acids (sour, putrid, animal) and alcohols (sweet, fruity, vegetable) are opposites.
Amines (animal) and aldehydes (vegetable) are opposites.
Amines (animal) and terpenes (vegetable) are opposites.
Consciousness>Consciousness>Sense>Smell>Odor
1-Consciousness-Sense-Smell-Odor
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Date Modified: 2022.0224