Phytochemistry Lecture 3: Volatile Oils
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Questions and Answers

Which of the following components is NOT found in volatile oils?

  • Oxygenated compounds
  • Hydrocarbons
  • Proteins (correct)
  • Aromatic benzenoids

What is one reason that terpeneless oils are considered more valuable?

  • They have a stronger turpentine aroma.
  • They are less soluble in low-strength alcohols.
  • They contain more terpenoid hydrocarbons.
  • They are more stable. (correct)

Which method is NOT used for the removal of terpenoid hydrocarbons?

  • Selective extraction with dilute alcohol
  • Column chromatography on silica gel
  • Fractional distillation under reduced pressure
  • Selective extraction with water (correct)

What characteristic of terpenoid hydrocarbons contributes to their rapid deterioration?

<p>Liability to oxidation and polymerization (D)</p> Signup and view all the answers

Isoprene units are characterized by which of the following?

<p>Being branched five-carbon units with two unsaturated bonds (B)</p> Signup and view all the answers

What is produced when cold dilute acids react with bicyclic monoterpenes?

<p>Terpineol and/or terpin hydrate (C)</p> Signup and view all the answers

Which reaction occurs when Sabinene is exposed to air and light?

<p>Yielding α-thujene (D)</p> Signup and view all the answers

What transformation occurs when bicyclic monoterpenes undergo treatment with acids?

<p>Ring-opening of the second cycle (C)</p> Signup and view all the answers

Which compound is obtained from the fractional distillation of oils from Juniperus sabina?

<p>Sabinene (C)</p> Signup and view all the answers

What type of compounds undergo molecular rearrangement, oxidation, and dehydrogenation?

<p>Bicyclic monoterpene hydrocarbons (A)</p> Signup and view all the answers

Which type of hydrocarbons makes up the majority of unoxygenated constituents in volatile oils?

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

What is the main process used to isolate non-phenolic fractions from volatile oils?

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

Which of the following compounds is recognized as a sesquiterpene analogue of myrecene?

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

Which component is predominantly found in citrus oils such as orange oil?

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

At what temperature is the fraction containing limonene collected during the fractional distillation process?

<p>176ºC (D)</p> Signup and view all the answers

Which of the following is NOT a use of limonene and dipentene?

<p>Solvents for paints (D)</p> Signup and view all the answers

Which of the following is considered a bicyclic monoterpenoid?

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

Which type of hydrocarbons can be categorized as both monocyclic and bicyclic?

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

Which of the following statements is true about terpenes?

<p>Terpenes can be either acyclic or cyclic in structure. (C)</p> Signup and view all the answers

What is the molecular formula of monoterpenoids?

<p>C10H16 (D)</p> Signup and view all the answers

Which term describes terpenes that are derived from the oxidation of bicyclic triterpenes?

<p>Irones (C)</p> Signup and view all the answers

Which of the following is NOT a type of volatile oil isolate?

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

Which of the following categories does NOT represent a classification of terpenes?

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

What structural feature is characteristic of phenyl propanoids found in essential oils?

<p>A 6-carbon aromatic phenyl group and a 3-carbon propene tail (A)</p> Signup and view all the answers

What is a common characteristic of acyclic sesquiterpenes and monocyclic sesquiterpenes?

<p>They are both C15 compounds. (B)</p> Signup and view all the answers

Which of the following statements about essential oils is true?

<p>Essential oils can contain both terpenoids and phenyl propanoids. (A)</p> Signup and view all the answers

What is the primary method used to obtain Santalene?

<p>Repeated fractional distillation (B)</p> Signup and view all the answers

Which essential oils are known sources of p-Cymene?

<p>Lemon, sage, thyme, and origanum (C)</p> Signup and view all the answers

Which statement best describes how p-Cymene is formed during hydro distillation?

<p>By cyclization and dehydrogenation of monoterpenoids (B)</p> Signup and view all the answers

What is the parent hydrocarbon that azulene derivatives are related to?

<p>C10H8 (B)</p> Signup and view all the answers

What effect do azulene derivatives exhibit?

<p>Anti-inflammatory and anti-ulcerative effects (B)</p> Signup and view all the answers

Which compound is NOT a product of the reduction of p-Cymene?

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

What is a common use of chamazulene?

<p>In cosmetic preparations for its anti-inflammatory properties (A)</p> Signup and view all the answers

What is the primary structure of azulene characterized by?

<p>Its highly conjugated structure (A)</p> Signup and view all the answers

What is the main constituent in oil of turpentine?

<p>α-Pinene (B)</p> Signup and view all the answers

Which compound is used in cough mixtures as a mucolytic?

<p>Sobrerol (C)</p> Signup and view all the answers

How is Zingiberene obtained from ginger oil?

<p>Fractional distillation under vacuum (B)</p> Signup and view all the answers

What process is used to convert α-Pinene into Sobrerol?

<p>Auto-oxidation (C)</p> Signup and view all the answers

Which product is obtained from the oxidation of Borneol?

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

Which two forms of oil of turpentine are specified based on their optical rotation?

<p>l-form and d-form (A)</p> Signup and view all the answers

What is a primary use of oil of cade?

<p>Anti-eczematic treatment (C)</p> Signup and view all the answers

Which derivative is formed through the reaction of α-Pinene with HCl gas?

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

Flashcards

Volatile Oil Composition

Volatile oils are mixtures of hydrocarbons (mono/sesquiterpenes), oxygenated compounds (alcohols, esters, aldehydes, ketones), aromatic benzenoids, and sulfur/nitrogen containing compounds.

Terpenoid Hydrocarbons

These are hydrocarbons that are easily oxidized/polymerized, leading to unwanted changes in the oil characteristics during storage.

Terpeneless Oil Preparation

A process to remove terpenoid hydrocarbons from volatile oils, improving storage stability and aroma quality.

Fractional Distillation

A method to separate volatile oil components based on their different boiling points, where compounds with lower boiling points (terpenes) are separated and removed.

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Isoprene

The building block for terpenoids; a branched five-carbon molecule with two unsaturated bonds.

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Terpenes Structure

Terpenes are organic compounds formed by the head-to-tail condensation of multiple isoprene units.

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Isoprene

A five-carbon molecule (C5H8) that acts as the fundamental structural unit for building terpenes.

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Monoterpenes

Terpenes composed of 10 carbon atoms (C10H16).

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Sesquiterpenes

Terpenes constructed from 15 carbon atoms (C15H24).

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Essential Oils Components

Essential oils are composed of a variety of compounds, including hydrocarbons, alcohols, phenols, aldehydes, ketones, oxides, and esters, derived from terpenes.

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Volatile Terpenes

Terpenes that easily evaporate and are present in essential oils. Usually hydrocarbons, alcohols, aldehydes and ketones.

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Phenylpropanoids

Natural products with a six-carbon aromatic ring (phenyl) and a three-carbon propene chain.

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Terpene Degradation Products

Compounds formed from the breakdown of terpenes, such as ionones and irons.

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Acyclic Monoterpenoids

Unbranched hydrocarbon compounds composed of two isoprene units in volatile oils.

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Alicyclic Monoterpenoids

Branched hydrocarbon compounds, composed of two isoprene units in volatile oils with cyclic/ring structures.

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Limonene

A monocyclic monoterpene hydrocarbon typically found in citrus oils.

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Myrcene

A volatile hydrocarbon found in oils from hops and bay trees.

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Fractional Distillation

Method for separating volatile oil components by different boiling points.

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Sesquiterpenes

Hydrocarbons containing three isoprene units in volatile oils.

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Farnesene

A volatile hydrocarbon (sesquiterpene) found in citronella oils.

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Dipentene

A monoterpene hydrocarbon often found alongside limonene in turpentine oil.

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p-Cymene Transformation

p-Cymene can undergo dehydrogenation and isomerization reactions, leading to the formation of other compounds like limonene and dipentene.

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Sabinene Double Bond Shift

Sabinene, exposed to air and light, undergoes a double bond shift to form α-thujene.

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Bicyclic Monoterpenes

These hydrocarbons, like fenchane, carane, pinane, and bornane, have tendency to rearrange, shift double bonds, undergo oxidation/hydrogenation, and ring-opening with acids.

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Terpineol/Terpin Hydrate Formation

Cold dilute acids can react with certain compounds to form terpineol and/or terpin hydrate.

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Carvone to Carveol

Carvone can be transformed into Carveol

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α-Pinene

A main component in turpentine oil, extracted through fractional distillation.

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Isomerization

Changing the structure of a molecule without altering its molecular formula.

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Borneol

A chemical compound resulting from oxidation of Pinene, used in pharmaceuticals.

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Zingiberene

Key compound in ginger oil, useful in perfumery.

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α-Pinene Auto-oxidation

Chemical transformation of α-pinene by oxidation in presence of water and sunlight.

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Sesquiterpenes

Terpenes with 15 carbon atoms; found in natural oils.

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ß-Cadinene

Bicyclic sesquiterpene hydrocarbon, often found in oils.

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Fractional Distillation

Separation of compounds in a mixture based on their different boiling points.

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Santalene

A v-Tricyclic sesquiterpenoid hydrocarbon obtained from Sandalwood oil through repeated fractional distillation.

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p-Cymene

An aromatic hydrocarbon often found in essential oils like lemon, sage, thyme, etc. It might form during the hydro-distillation process.

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Sesquiterpenes

Hydrocarbons made up of three isoprene units and 15 carbon atoms.

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Azulene

A C10H8 hydrocarbon with highly conjugated properties (colored) found in some mushrooms, guaiac wood oil, and marine sources.

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Chamazulene

Blue-colored derivative of azulene, obtained from chamomile oil, and used in cosmetics.

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Essential Oils

Plant extracts containing various compounds, including hydrocarbons, oxygenated compounds, and aromatic benzenoids, commonly used to perfume and heal.

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Semi-synthesis

Conversion of one known compound into another compound via various chemical processes, to create specific chemicals.

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Fractional Distillation

Technique to separate components of a mixture based on differences in boiling points, as applied to oil extraction.

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Study Notes

Phytochemistry Lecture 3: Chemistry of Volatile Oils Constituents

  • Volatile oils are complex mixtures of organic compounds.
  • Crucial components include hydrocarbons (mono and sesquiterpenes), oxygenated compounds (alcohols, esters, aldehydes, ketones), aromatic benzenoids, and compounds with sulfur or nitrogen.
  • Oxygenated compounds are responsible for the characteristic odor of volatile oils.

Removal of Terpenoid Hydrocarbons (Preparation of Terpeneless Oil)

  • Oils high in terpenoids are prone to rapid oxidation and polymerization during storage, leading to undesirable (turpentine-like) odors and reduced aroma.
  • These oils are less soluble in low-strength alcohols and often resenify quickly.
  • Terpene-less oils are more stable and more soluble in low-strength alcohols, requiring less material to achieve the same aroma strength. They contain richer amounts of oxygenated compounds.
  • Methods to remove terpenoid hydrocarbons include fractional distillation under reduced pressure, column chromatography (using silica gel and solvents), and selective extraction using dilute alcohol.

Terpenoids

  • Terpenoids are synthesized from isoprene.
  • Isoprene is also known as isopentene or 2-methyl-buta-1,3-diene.
  • Isoprene units are branched five-carbon units containing two unsaturated bonds.
  • Terpenes arise from the head-to-tail condensation of a variable number of isoprene units.
  • Different types of terpenes exist, including monoterpenes (C10), sesquiterpenes (C15), and others.
  • Chemical structures are displayed for various types of terpenes.

Terpenoids in Essential Oils

  • Monoterpenoids (C10H16) and sesquiterpenoids (C15H24).
  • These may exist in acyclic (non-cyclic) or alicyclic (cyclic) forms.
  • Many are hydrocarbons (90% of some citrus oils), as well as oxygenated forms (alcohols, aldehydes, ketones, esters, ethers, oxides, or peroxides).
  • Many terpenoids are optically active.
  • Some terpenes break down into other compounds due to oxidation.

Phenylpropanoids in Essential Oils

  • Natural products in volatile oils.
  • Contain a 6-carbon aromatic phenyl group and 3-carbon propene tail.
  • Exhibit pharmacological properties and are used in the pharmaceutical industry.
  • Examples include various hydrocarbons, alcohols, phenols, phenolic ethers, aldehydes, ketones, oxides, peroxides, and esters.

Hydrocarbons in Volatile Oils

  • These are unoxygenated constituents.
  • Includes various types of mono- and sesqui-terpenoids.
  • Acyclic and alicyclic forms are noted, including monocyclic, bicyclic, and tricyclic forms.
  • Aromatic hydrocarbons are also present.

Acyclic Terpenoids

  • Includes monoterpenoid and sesquiterpenoid hydrocarbons, such as myrecene and ocimene.

Alicyclic Sesquiterpenoids

  • Includes sesquiterpenoid hydrocarbons, such as farnesene and sesquicitronellene.

Alicyclic Terpenoid Hydrocarbons

  • Forms of monoterpenes (e.g., monocyclic, bicyclic), and sesquiterpenes (e.g., monocyclic, bicyclic, tricyclic)

Monocyclic Monoterpenoid Hydrocarbons

  • d-Limonene (citrus oils).
  • l-Limonene (turpentine oil).
  • Dipentene (dl form – racemic), (turpentine oil)

Bicyclic Monoterpene Hydrocarbons

  • Thujane derivatives, including sabinene.
  • ß-Pinane derivatives, including a-pinene and ß-pinene.

Monocyclic Sesquiterpenoid Hydrocarbons

  • Zingiberene (main constituent of ginger oil).

Bicyclic Sesquiterpenoid Hydrocarbons

  • Naphthalene derivatives, including cadinene and zingiberene.

Tricyclic Sesquiterpenoid Hydrocarbons

  • Santalene (obtained from sandalwood oil by repeated fractional distillation)

Aromatic Hydrocarbons

  • p-Cymene.
  • Source, isolation, and uses described.

Semi-synthesis

  • Methods to transform one compound into another.
  • Example reactions to form new chemical structures are shown.

Azulene Derivatives

  • Highly conjugated pigments found in mushrooms, guaiac wood oil.
  • Mostly colorless pro-azulenes
  • Isolation via adducts with mineral acids.
  • Parent hydrocarbon is azulene (C10H8).
  • Naturally occurring azulenes are substituted with alkyl groups (C15 compounds).
  • Exhibit anti-inflammatory and anti-ulcerative effects.
  • Example compounds: Chamazulene and Guaiazulene.

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Phytochemistry Lecture 3 PDF

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Explore the chemistry of volatile oils and their constituents in this lecture. Learn about the composition of volatile oils including terpenoids and the methods used to prepare terpeneless oils for better stability and aroma. This quiz will help reinforce your understanding of these essential oils in phytochemistry.

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