The clove had little or no discernible smell until you sliced it allowing these two compounds to mix and form a third compound, diallyl thiosulphinate, commonly called allicin. Among researchers, there are several other complicated chemical names for allicin. It is the allicin that is thus formed by chemical action that has the familiar garlic smell. In a matter of hours it will further degrade into an oily witches brew of bisulphides, trisulphides such as methyl allyl trisulphide and methanethiol and polysulphides and many others. Allicin exists only in raw garlic and cooking kills it and causes it to decay into other compounds which are either less antibiotic or not at all antibiotic in nature.
Raw garlic contains no oil.
Oil is not formed until garlic is crushed and then degrades down into the oily mix of sulfurous compounds, described above. The more time that elapses after crushing, the more complex the compounds become and the less sulfurous they smell. The simpler sulfur compounds have the most smell and the most anti-bacterial action. The polysulphides which are among the last breakdown products of allicin have the least taste and smell and the least medicinal effects. It is the allicin which is garlic's natural protection from pests and diseases and when we eat the fresh garlic it protects us also.