Chemistry of Natural Products (PHG 322)
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Questions and Answers

What type of odour do ketones have?

  • Strong and pungent odour
  • Sweet and fruity odour
  • Pleasant odours (correct)
  • Foul odour

What specific odour is associated with nitriles?

  • Bitter almond odour (correct)
  • Peppery odour
  • Citrus odour
  • Floral odour

Which isomer of carvone is associated with the odour of spearmint?

  • s-carvone
  • m-carvone
  • l-carvone (correct)
  • d-carvone

Which of the following is true regarding isomers and odours?

<p>Different isomers may produce different odours (C)</p> Signup and view all the answers

What odour is characterized by d-carvone?

<p>Caraway odour (A)</p> Signup and view all the answers

What is the numerical value associated with 'Tri' compounds?

<p>30 (A)</p> Signup and view all the answers

Which type of compounds are primarily responsible for the characteristic odor of oil?

<p>Oxygenated compounds (B)</p> Signup and view all the answers

In the given classification, how many variations are there in the 'Di' category?

<p>20 (B)</p> Signup and view all the answers

What do both oxygenated and non-oxygenated groups of compounds have in common?

<p>They are included in the same classifications. (A)</p> Signup and view all the answers

Which of the following best describes hydrocarbons within these classifications?

<p>They include both oxygenated and non-oxygenated members. (C)</p> Signup and view all the answers

At what temperature does oil of anise begin to solidify?

<p>15°C (D)</p> Signup and view all the answers

Which oil remains non-volatile and leaves a gummy residue?

<p>Oil of Lemon (A)</p> Signup and view all the answers

What is the solidification temperature for oil of rose?

<p>18°C (A)</p> Signup and view all the answers

Which of the following oils solidifies at a higher temperature compared to oil of anise?

<p>Oil of Rose (C)</p> Signup and view all the answers

What characteristic makes a substance more soluble in low strength alcohol?

<p>Smaller molecular size (B)</p> Signup and view all the answers

Which statement is true regarding oil of anise?

<p>It solidifies below 15°C. (C)</p> Signup and view all the answers

What is significant about the amount used for the same strength of aroma?

<p>A smaller amount is used compared to other solvents (C)</p> Signup and view all the answers

What is the implication of being richer in oxygenated compounds?

<p>It can enhance the aroma and flavor profile (D)</p> Signup and view all the answers

Which factor does not contribute to the solubility of a substance in low strength alcohol?

<p>Overall molecular weight (C)</p> Signup and view all the answers

How does the presence of oxygenated compounds affect the usage of a substance?

<p>It allows a smaller quantity to achieve the same aroma strength (A)</p> Signup and view all the answers

What effect does high terpenoid content have on the aroma of oils?

<p>It decreases the aroma. (D)</p> Signup and view all the answers

Which of the following is a characteristic of terpeneless oils compared to natural oils?

<p>They are more stable. (A)</p> Signup and view all the answers

How does high terpenoid content affect the solubility of oil in low-strength alcohols?

<p>It decreases solubility. (A)</p> Signup and view all the answers

What is the consequence of high terpenoid content in oils, besides decreasing aroma?

<p>It causes rapid resinification. (A)</p> Signup and view all the answers

What can be said about the cost comparison between terpeneless oils and natural oils?

<p>Terpeneless oils are more expensive than natural oils. (D)</p> Signup and view all the answers

What is the initial phase of the chromatography process described?

<p>Elution of hydrocarbons with n-hexane (A)</p> Signup and view all the answers

Which solvent is used to elute oxygenated compounds in the chromatography process?

<p>Absolute alcohol (A)</p> Signup and view all the answers

What method is used for the selective extraction of oxygenated components after chromatography?

<p>Dilute alcohol extraction (B)</p> Signup and view all the answers

What follows the selective extraction of oxygenated components in the described process?

<p>Distillation (D)</p> Signup and view all the answers

What type of compounds are initially eluted using n-hexane in the chromatography process?

<p>Hydrocarbons (B)</p> Signup and view all the answers

Flashcards

Solid below room temperature

A substance like oil of anise that becomes solid at temperatures below room temperature (15°C).

Solidification point

The point at which a substance changes from a liquid to a solid state. For oil of anise, this is below room temperature (15°C).

Oil of rose solidification

The solidification point of oil of rose is 18°C, meaning it changes from a liquid to a solid state below this temperature.

Non-volatile residue

Oil of lemon, unlike many other essential oils, leaves a thick, sticky residue when it evaporates.

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Non-volatile substance

A substance that does not readily evaporate at room temperature, like oil of lemon, which leaves a gummy residue behind.

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Ketones

Ketones are a class of organic compounds that contain a carbonyl group (C=O) bonded to two alkyl groups. This chemical structure is responsible for their pleasant smell.

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Nitriles

Nitriles are organic compounds containing a cyano group (C≡N) attached to an alkyl or aryl group. They possess a distinctive odour.

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Isomers and Odor

Isomers are molecules with the same molecular formula but different spatial arrangements of atoms. This structural difference can lead to variations in their physical and chemical properties, including odor.

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Enantiomers and Odor

d-Carvone and l-Carvone are examples of enantiomers, a type of isomer where molecules are mirror images of each other. Their different 3D structures influence their scent perception.

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Stereochemistry and Odor

The specific spatial arrangement of atoms within a molecule, known as its stereochemistry, can significantly influence its odor. This is because the shape of the molecule impacts how it interacts with odor receptors in our nose.

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Soluble in low strength alcohol

Essential oils that dissolve better in weak alcohol solutions.

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Smaller amount for aroma strength

A smaller amount of this type of essential oil is needed to achieve the same intensity of aroma.

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Rich in oxygenated compounds

Essential oils containing a higher proportion of oxygen-containing compounds.

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Aroma strength

The characteristic scent of an essential oil

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Solubility in alcohol

The process of dissolving an essential oil in alcohol.

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Essential Oil Groups

Essential oils are classified into 'groups' based on the number of carbon atoms in their molecules. These groups are named using prefixes like "Mono", "Di", and "Tri", indicating 10, 20, and 30 carbon atoms, respectively.

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Oxygenated vs. Non-Oxygenated Compounds

Each group of essential oils includes both oxygenated and non-oxygenated compounds. Non-oxygenated compounds are often called hydrocarbons.

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Oxygenated Compounds and Odor

The oxygenated compounds within an essential oil group are generally responsible for the characteristic scent or aroma of the oil.

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Classifying Essential Oils

Essential oils are classified into 'groups' based on the number of carbon atoms in their molecules, with prefixes indicating carbon count: "Mono" - 10, "Di" - 20, "Tri" - 30. Within each group, there are both oxygenated and non-oxygenated compounds, with oxygenated compounds primarily responsible for the oil's scent.

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Essential Oil Components

Essential oils contain both oxygenated and non-oxygenated components. Oxygenated components contribute to the oil's aroma, while non-oxygenated components are primarily hydrocarbons.

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Terpenoids and Aroma

Terpenoid content in essential oils can lead to a decrease in the oil's aroma due to its impact on the volatile compounds responsible for the scent.

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Terpenoids and Solubility

A high concentration of terpenoids in essential oils makes them less soluble in low-strength alcohols, leading to a separation of the oil and alcohol.

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Terpenoids and Resinification

Elevated terpenoid content in an essential oil can accelerate the process of resinification, causing the oil to thicken and form a sticky residue.

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Terpeneless Oils

Terpeneless oils are produced by removing terpenes from natural oils. This process makes the oils more stable and less prone to changes over time.

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Terpeneless Oil Cost

While terpeneless oils offer greater stability, they are usually more expensive than their natural counterparts due to the additional processing involved.

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Column Chromatography

A separation technique used to isolate components of a mixture based on their differing affinities for a stationary phase (silica gel) and a mobile phase (solvents). The mobile phase moves through the stationary phase, carrying different components at different rates, resulting in their separation.

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n-Hexane

A solvent commonly used in column chromatography to elute (separate) hydrocarbons, which are non-polar compounds. Its low polarity helps to weakly interact with the stationary phase and allow hydrocarbons to move faster.

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Absolute Alcohol

A solvent commonly used in column chromatography to elute oxygenated compounds, which are more polar. Its higher polarity allows it to interact more strongly with the stationary phase, slowing down the oxygenated compounds and separating them from hydrocarbons.

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Selective Extraction

A technique used to selectively isolate oxygenated compounds from a mixture by using a solvent (dilute alcohol) that preferentially interacts with these compounds. The solvent is then removed by distillation, leaving behind the concentrated oxygenated compounds.

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Distillation

Separation technique used to purify liquids by vaporizing them and then condensing the vapor, removing impurities. The compounds with different boiling points vaporize and condense at different temperatures, leading to their separation.

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Study Notes

Chemistry of Natural Products (PHG 322)

  • This course covers the chemistry of volatile oils
  • Instructors are Shahira Ezzat, PhD and Mahitab Helmi, PhD
  • Both are professors of Pharmacognosy at MSA University

Learning Outcomes

  • Define and classify volatile oils
  • Understand the physical characteristics of volatile oils
  • Recognize the chemical composition of volatile oils
  • Recognize the natural sources, chemical structures, pharmacological actions and therapeutic uses of volatile oil isolates belonging to the hydrocarbon class
  • Identify methods for isolating and determining volatile oil isolates belonging to the hydrocarbon class

Interactive Teaching Methods

  • Socrative

Volatile Oils

  • Volatile oils are fragrant liquids
  • They evaporate easily at room temperature
  • Also called essential oils or ethereal oils

Definition

  • Complex liquid mixtures of odoriferous principles
  • Primarily derived from plant sources, rarely animal sources
  • Varying chemical composition
  • Easily evaporate at ordinary temperatures
  • Used for therapeutic activity or aroma

Medicinal and Commercial Uses

  • Therapeutic uses: local stimulants, carminatives, diuretics, mild antiseptics, local irritants, anthelmintics, parasiticides
  • Spices and condiments: flavoring and preserving food
  • Flavoring agents: used in beverages, soups, bakery products, and confectionery
  • Aromatic agents: used in perfumes, cosmetics, soaps, deodorizers, household cleaners, polishes, and insecticides

Common Physical Characters

  • Colorless, pleasant smelling liquids
  • Volatile at room temperature
  • Steam distillable
  • High refractive index
  • Mostly optically active
  • Density generally less than water
  • Immiscible with water, but sufficiently soluble to impart a fragrance to water (aromatic waters)
  • Soluble in alcohol and common organic solvents
  • May darken in color when exposed to air and light (resinification)

Exceptions

  • Oils containing azulenes (e.g., chamomile) are colored
  • Rose oil is turbid due to paraffin hydrocarbons
  • Some oils solidify below room temperature (e.g., anise, rose)
  • Lemon oil is a non-volatile gummy residue
  • Some oils (cinnamon, clove, wintergreen) are denser than water

Chemical Composition of Volatile Oils

  • Complex chemical mixtures
  • Vary widely in chemical composition
  • Include hydrocarbons, alcohols, ketones, aldehydes, ethers, oxides, phenols, and esters
  • Some oils consist mainly of a single compound (e.g., mustard oil, clove oil).

Relationship between Chemical Structure and Odour

  • Compounds with different structures can sometimes have similar odors.
  • Odor can change with dilution
  • Ex: Indole, pleasant in small concentrations, has a putrefaction odor otherwise.
  • Aldehydes have strong odors, esters have fruity odors, ketone odors are pleasant, nitriles have bitter almond odor
  • Different isomers may have distinct odors, Ex: d-carvone (caraway) vs 1-carvone (spearmint).

Chemistry of Volatile Oils Constituents: Composition of Volatile Oil

  • Composition is complex.
  • Primarily from hydrocarbons, terpenoids, phenyl propanoids etc.

Terpenoids

  • Synthesized from isoprene
  • Isoprene is also called isopentene or 2-methylbuta-1,3-diene
  • Branched five-carbon units with two unsaturated bonds
  • Biosynthesized from variable numbers of isoprene units via head-to-tail condensation

Sesquiterpenes (C15)

  • Acyclic sesquiterpenes
  • Monocyclic sesquiterpenes

Terpenoids in Essential Oils

  • Monoterpenoids (C10H16): Acyclic, Alicyclic, hydrocarbons,oxygenated (alcohols, aldehydes, ketones etc.), optically active
  • Sesquiterpenoids (C15H24): Acyclic, Alicyclic, hydrocarbons,oxygenated (alcohols, aldehydes, ketones etc.), optically active
  • Compounds arising from terpene degradation (ionones, irons)
  • Phenyl propanoids: less common,phenols, pheol ethers, aldehydes, lactones
  • Terpenoid Hydrocarbons in Oils: Volatile oil characteristics (low mol wt) , high terpene content may lead to bad odor and resinification. Decrease aroma, decrease odor solubility in alcohol, rapid resinification.

The Isoprene Rule

  • Classification of terpenoids based on the number of isoprene units
  • Hemiterpenoids, Monoterpenoids, Sesquiterpenoids, Diterpenoids, Triterpenoids, Tetraterpenoids
  • Examples given for each class

Removal of Terpenoid Hydrocarbons

  • Fractional distillation
  • Column chromatography (using silica gel and solvents)
  • Selective extraction (using dilute alcohol)

Volatile Oil Isolates

  • Physical methods: Cooling, Fractional Distillation, Preparative Chromatography
  • Chemical methods: Formation of soluble salts, Derivatization, Adduct formation
  • Compounds formed: Hydrocarbons, Alcohols, Phenols, Aldehydes, Ketones, Oxides, Peroxides, Esters, Organo-nitrogen&Organo-sulfur compounds

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Chemistry of Natural Products (PHG 322) Lecture Notes (MSA University) PDF

Description

This quiz assesses your understanding of volatile oils, including their definition, classification, and chemical characteristics. You will explore natural sources, pharmacological actions, and therapeutic uses of these essential oils, as well as methods for their isolation. Test your grasp of this intricate field of chemistry!

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