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Questions and Answers
What type of odour do ketones have?
What type of odour do ketones have?
What specific odour is associated with nitriles?
What specific odour is associated with nitriles?
Which isomer of carvone is associated with the odour of spearmint?
Which isomer of carvone is associated with the odour of spearmint?
Which of the following is true regarding isomers and odours?
Which of the following is true regarding isomers and odours?
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What odour is characterized by d-carvone?
What odour is characterized by d-carvone?
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What is the numerical value associated with 'Tri' compounds?
What is the numerical value associated with 'Tri' compounds?
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Which type of compounds are primarily responsible for the characteristic odor of oil?
Which type of compounds are primarily responsible for the characteristic odor of oil?
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In the given classification, how many variations are there in the 'Di' category?
In the given classification, how many variations are there in the 'Di' category?
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What do both oxygenated and non-oxygenated groups of compounds have in common?
What do both oxygenated and non-oxygenated groups of compounds have in common?
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Which of the following best describes hydrocarbons within these classifications?
Which of the following best describes hydrocarbons within these classifications?
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At what temperature does oil of anise begin to solidify?
At what temperature does oil of anise begin to solidify?
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Which oil remains non-volatile and leaves a gummy residue?
Which oil remains non-volatile and leaves a gummy residue?
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What is the solidification temperature for oil of rose?
What is the solidification temperature for oil of rose?
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Which of the following oils solidifies at a higher temperature compared to oil of anise?
Which of the following oils solidifies at a higher temperature compared to oil of anise?
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What characteristic makes a substance more soluble in low strength alcohol?
What characteristic makes a substance more soluble in low strength alcohol?
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Which statement is true regarding oil of anise?
Which statement is true regarding oil of anise?
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What is significant about the amount used for the same strength of aroma?
What is significant about the amount used for the same strength of aroma?
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What is the implication of being richer in oxygenated compounds?
What is the implication of being richer in oxygenated compounds?
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Which factor does not contribute to the solubility of a substance in low strength alcohol?
Which factor does not contribute to the solubility of a substance in low strength alcohol?
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How does the presence of oxygenated compounds affect the usage of a substance?
How does the presence of oxygenated compounds affect the usage of a substance?
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What effect does high terpenoid content have on the aroma of oils?
What effect does high terpenoid content have on the aroma of oils?
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Which of the following is a characteristic of terpeneless oils compared to natural oils?
Which of the following is a characteristic of terpeneless oils compared to natural oils?
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How does high terpenoid content affect the solubility of oil in low-strength alcohols?
How does high terpenoid content affect the solubility of oil in low-strength alcohols?
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What is the consequence of high terpenoid content in oils, besides decreasing aroma?
What is the consequence of high terpenoid content in oils, besides decreasing aroma?
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What can be said about the cost comparison between terpeneless oils and natural oils?
What can be said about the cost comparison between terpeneless oils and natural oils?
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What is the initial phase of the chromatography process described?
What is the initial phase of the chromatography process described?
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Which solvent is used to elute oxygenated compounds in the chromatography process?
Which solvent is used to elute oxygenated compounds in the chromatography process?
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What method is used for the selective extraction of oxygenated components after chromatography?
What method is used for the selective extraction of oxygenated components after chromatography?
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What follows the selective extraction of oxygenated components in the described process?
What follows the selective extraction of oxygenated components in the described process?
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What type of compounds are initially eluted using n-hexane in the chromatography process?
What type of compounds are initially eluted using n-hexane in the chromatography process?
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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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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!
