Exploring the Chemical Compounds that Make up Different Aromas of Life

9 months ago

Have you ever stepped into a bookstore or library and been greeted by that unmistakable scent, unique to books alone? It's that faint musty fragrance, often tinged with hints of vanilla or coffee, or perhaps reminiscent of freshly cut grass. Personally, I've often experienced this scent when perusing bookshops, and it's as if that crisp, inviting aroma tempts me to linger a little longer among the shelves.

Our olfactory senses can detect an array of scents, ranging from the sweet to the putrid, the fresh to the pungent. These aromas are composed of intricate chemical compounds. When it comes to books, this captivating scent is derived from various compounds found in the paper, ink, and bindings of the book. We often hear that paper is made from wood pulp, which itself consists of numerous organic chemical compounds containing carbon atoms. It is made up of cellulose (a long chain of glucose molecules) bounded by Lignin (polymer) which then releases volatile organic compounds when they react with light, heat, and moisture as they break down.

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The type of VOC you detect in your book can be determined by how the manufacturer make the paper and the bind. The VOC can range from Benzaldehyde which smells like almond, Vanillin which gives the vanilla smell, Ethybenzene which gives the sweet smell. There's also 2-ethyl hexanol, contributing a floral smell. Different paper manufacturers employ distinct chemicals, including hydrogen peroxide for bleaching paper and alkyl ketene dimers to enhance water resistance.

You see, while I will say I usually find book smell appealing, although VOCs can be dangerous to health, I find rain more appealing and it looks like it has a very distinctive smell. While water itself is odorless, it carries with it the fragrance of freshness and cleanliness, which stems from the oils present in plants. This enchanting aroma is known as petrichor, emanating from plant oils rich in fatty acids like palmitic and stearic acids. These oils on the plant, on soils, rocks, or dirts, find their way to the air as rain fall to the surface giving the fragrant VOCs.

When you smell the earth, it gives this earthy smell known as Geosmin which is released by bacteria like Streptomyces when they die, and when it is raining the chemical smell also evaporates into the air. Also, people can smell ozone before it even begins to rain. It occurs when lightening ionizes a molecule of oxygen in the air causing it to combine with oxygen to give O3 which has a sharp bracing scent.

Speaking of scents, I can't help but mention the exhilarating aroma that arises when grass is mowed. It's a fragrance that evokes the essence of spring and renewal, tempting you to linger in the vicinity (unless, of course, bugs are chasing you away). This aroma is released by injured plants, who emit organic compounds known as Green Leaf Volatiles (GLVs) which includes aldehydes, alcohols, and esters, and they are to invite predators of grass eating insects to come eat the insects feeding on them or causing them injuries. The chemicals includes Salicylic Acid and Jasmonic Acid which help the plant synthesize compounds that make them less attractive as well as prevent fungi and bacteria infection, Traumatic acid signals the plant to make more cells to close the wound.

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Yet another scent to ponder is that distinctive fragrance within a car's interior. While this scent can be pleasing, it's essential to realize that these are VOCs. Though some VOCs may pose minimal health risks, others can be perilous. The new-car smell that accompanies your vehicle purchase is actually off-gassing from components such as glues, paints, upholstery, leather, and plastics. New vehicles tend to off-gas more releasing more than 30 VOCs such as styrene, acetaldehyde, benzene, and even formaldehyde into the atmosphere. Styrene, acetaldehyde, benzene, and formaldehyde are carcinogens and could cause cancer.

The world is indeed a trove of intriguing aromas, from the pungent scent of a petrol station to the cool, earthy fragrance of brick walls. I invite you to share your experiences with specific scents tied to particular places or objects, maybe we can both breakdown what releases those chemicals and the chemicals themselves.