How does pentanol smell

Chemistry internship grade 11

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Topic: Esters - fragrances and flavorings


Almost all esters have a pleasant odor. Many different, mostly short-chain esters together make up the aroma of fruits and flowers. They are a comparatively simple type of flavoring substance. Some are also used as solvents in adhesives. Long-chain esters are e.g. fats.

The production of esters requires acid (carboxylic acid or inorganic acid) and alcohol. These substances hardly react by themselves over the burner flame, which is why a catalyst is still required. One of the best-known esters is acetylsalicylic acid ethyl ester, better known as aspirin. The polymer polyester is widely used in the textile industry.

The functional group of the carboxylic acids is the COOH group (carboxyl group).
An overview of the most important of these acids:

Methanoic acid
Formic acid
Ethanoic acid
acetic acid
Propanoic acid
Propionic acid
Butanoic acid
Butyric acid
Pentanoic acid
Valeric acid
Hexanoic acid
Benzoic acid
Dodecanoic acid
Lauric acid
Hexadecanoic acid
Palmitic acid
Octadecanoic acid
Stearic acid

With increasing length, the molecules of the carboxylic acids lose polarity, making them less soluble in water and more soluble in gasoline.

Tasks and glossary

  1. What are the terms perfume, fragrance and flavoring?

    A perfume is an animal or synthetically produced aqueous-alcoholic solution from predominantly herbal fragrances. In addition, a fixator is included so that the fragrance lasts longer.
    Fragrances are defined as chemical substances that stimulate the senses of smell and are used e.g. for communication in animals and for attracting / deterring plants.
    Flavorings are either naturally occurring or industrially produced additives that are present in almost all foods to enhance or impart flavor.
  2. When can you call a fragrance natural? What is a nature-identical and what is an artificial fragrance?

    Natural fragrances
    Natural fragrances are naturally occurring, not artificially produced substances or mixtures of substances.
    Nature-identical fragrances
    A nature-identical fragrance is synthetically produced, but has the same properties as the natural ones, e.g. vanillin.
    Artificial fragrances
    Artificial fragrances do not occur naturally in this way. They are developed in the laboratory.
  3. When, where and in what form do we come into contact with fragrances and aromas on a daily basis?

    Even in the morning at breakfast you encounter the first aromatic substances in food. On the way to work, especially in smokers' cars, the scent of an air freshener may rise. Fragrance dispensers can also be found in many other places, especially at home. However, they are suspected of making you sick.
  4. "Our sense of smell is a secret, but extremely purposeful sales advisor." Is this true? Is this used deliberately for manipulation?

    When shopping you have an exact idea of ​​what you want, but smells make you consciously and unconsciously tend towards certain products. There are already small black boxes in many shops that are supposed to stimulate the desire to buy by secreting certain odorous substances.
  5. Which chewing gum flavor is currently “in”? Has this changed?

    Nowadays, flavor combinations of “refreshing fruits (e.g. lemons or grapefruit) are chewed in conjunction with mint. Older varieties such as “Juicyfruit” or “Hubba Bubba”, which have a strong taste of different types of fruit, are still available, but are no longer as popular. The taste of mint chewing gum usually lasts longer than the taste of others.
  6. Which fragrances do younger and older people prefer?

    Older people may prefer "classic" local scents such as lavender. Younger people like more exotic things like citrus fruit flavors.
  7. Nature holds an abundance of fragrant and aromatic plants ready. Which plants provide fragrances or aromas?

    These include lavender, roses, cherries, almonds, oranges and cloves.
  8. From the animal kingdom, only four fragrance raw materials are important for perfume production. These are: musk, ambergris, civet and castoreum (Bibergeil). Which animals produce these fragrances and how are these substances obtained? What tasks do these substances perform in the animal world?

    Ambergris is the excretion of the sperm whale. It can be found floating in the ocean and in dead whales. Castoreum is also known as Bibergeil, the beaver's sex secretion. In order to win it, the animals are killed. Musk is the sex secretion of the musk deer. You have to kill the animal to get the substance. Civet is the marking secretion of the civet cat and is taken from living animals.
    Amber and musk can now be produced synthetically. There are very similar substitutes for castoreum and civet.
    In the animal world, they are mostly used as attractants or to mark the territory. They are very common in perfumes.
  9. Most flowers and leaves have a low yield of essential oils. Five tons of rose petals only make 1kg of rose oil. What is the mass of a single rose blossom (estimated)? How many flowers do you need for 1kg of rose oil?

    Depending on the water content, which is highest shortly after picking, a flower weighs around 15g. You need 333333 of it to make 1kg of rose oil. Like all other concentrated oils, this is heavily diluted, otherwise the smell would be too extreme and unaffordable. The price is around 5000 euros per kg.
  10. What methods of winning fragrances are there? Advantages and disadvantages?

    The Enfleurage and Maceration are no longer used today. This type of extraction is too expensive and not very productive. The distillation with steam is possible everywhere and without great effort. But where heat is generated, fragrances and dyes can be destroyed. It is best to use the material to squeeze out, because all substances remain unchanged.

Experiment: Synthesis of fragrant esters

With the help of various acids and alcohols, esters are to be produced.

You put a spatula with any acid and some alcohol in a test tube. Then add a few drops of sulfuric acid. This serves as a catalyst. The test tube is now heated over the burner and an odor sample is fanned out.

Observations, scent impressions & evaluation:
The mostly stinking acids turn into a fragrant substance during esterification and water is created as a by-product. The liquid sometimes turns pink after heating.

The following combinations were tried:

acidalcoholReaction productMolecular formulaodoruse
Formic acidButanolButyl methanoateH-COO-C4H9 H-COO-C4H9RosesFragrance
acetic acidPropanolPropyl ethanoateCH3-COO-C3H7 CH3-COO-C3H7fruitFlavoring agent
Propionic acidPentanolPentyl propanoateC.2H5-COO-C5H11 C2H5-COO-C5H11blossomsFragrance
Butyric acidMethanolButanoic acid methyl esterC.3H7-COO-CH3 C3H7-COO-CH3pineappleFlavoring agent
Butyric acidEthanolEthyl butanoateC.3H7-COO-C2H5 C3H7-COO-C2H5peachFlavoring agent
Valeric acidMethanolMethyl pentanoateC.4H9-COO-CH3 C4H9-COO-CH3bananaFlavoring agent
Valeric acidPentanolPentyl pentanoateC.4H9-COO-C5H11 C4H9-COO-C5H11AppleFlavoring agent
Benzoic acidPropanolPropyl heptanoateC.5H11-COO-C3H7 C5H11-COO-C3H7fruitFragrance

Error consideration:
Due to the very high concentration of the esters, it is difficult to clearly assign the fragrances. In addition, the many different smells sometimes overlap, especially if another group has caused a delay in boiling.

The pink color of the final product may be due to badly cleaned test tubes.

Additional information beyond the level of the 11th grade

Alcohols and carboxylic acids react to form esters and water. However, a reverse reaction also takes place until a chemical equilibrium is finally established. By withdrawing the water that is produced during the forward reaction, this equilibrium can be shifted so that the yield of esters is even higher.

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