Chemistry of Esters

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Questions and Answers

Why must oil be free from organic acids before vacuum distillation?

To improve the color of the oil

To enhance the flavor of the oil

To increase the boiling point of the oil

To prevent the hydrolysis of the ester (correct)

What process is used to identify esters?

Saponification (correct)

Distillation

Filtration

Preciptation

What will likely happen if organic acids are present during the distillation of oil?

Color change in the oil will be accelerated

The boiling point will decrease

The oil will become solid

Ester hydrolysis can occur (correct)

Which of the following is a consequence of ester hydrolysis during distillation?

Formation of acids and alcohols Signup and view all the answers

What is the primary goal of using vacuum during fraction distillation of oil?

To facilitate separation at lower temperatures Signup and view all the answers

What is one primary use of Gaultherin?

Natural substitute of Aspirin Signup and view all the answers

Which property is associated with Methyl salicylate?

Antiseptic Signup and view all the answers

What function does Gaultherin serve in terms of inflammation?

Cyclo-oxygenase inhibition Signup and view all the answers

Which of the following is NOT a property of Methyl salicylate?

Cyclo-oxygenase inhibition Signup and view all the answers

What role does Methyl salicylate play in dental care?

Anticariogenic agent Signup and view all the answers

What complex is formed during the isolation of the substance described?

Na bisulfite complex Signup and view all the answers

What happens to the substance when exposed to air?

It is converted to phellandric acid Signup and view all the answers

Which property indicates that the substance has potential use against microorganisms?

It has antimicrobial activity Signup and view all the answers

What physical state is described for the substance?

It is oil Signup and view all the answers

What is a characteristic property of the substance related to its stability?

It is readily oxidized Signup and view all the answers

What type of infections do powerful broad-spectrum agents combat?

Various types of infections, including viral and parasitic Signup and view all the answers

Which of the following is NOT a characteristic of broad-spectrum agents?

Highly targeted Signup and view all the answers

How is the immune system described in relation to powerful broad-spectrum agents?

It is stimulated by these agents Signup and view all the answers

Which of the following does NOT relate to the use of powerful broad-spectrum agents?

Narrow-spectrum effectiveness Signup and view all the answers

What is an additional benefit of using broad-spectrum agents mentioned in the content?

Acts as a general tonic Signup and view all the answers

What is the appearance of the isolated product from Cassia and cinnamon oils?

A yellow liquid Signup and view all the answers

What odor is characteristic of the isolated product from Cassia and cinnamon oils?

A cinnamon odor Signup and view all the answers

What transformation occurs to the product when it is exposed to air?

It is partially oxidized to cinnamic acid Signup and view all the answers

How is the product from Cassia and cinnamon oils regenerated?

By using Na2CO3 Signup and view all the answers

Which chemical complexes are used to isolate the product from Cassia and cinnamon oils?

Complexes with sodium sulfite or bisulfite Signup and view all the answers

What is deposited on the filter paper disc during the combustion test?

Oil Signup and view all the answers

What is used to moisten the inner surface of the inverted beaker in the combustion test?

Distilled water Signup and view all the answers

In the combustion test, where is the filter paper disc placed?

In a porcelain dish Signup and view all the answers

What is the primary purpose of the combustion test?

To accurately test the oil Signup and view all the answers

What happens to the beaker during the combustion test?

It is inverted over the dish Signup and view all the answers

Study Notes

Esters

Many volatile oils get their odor and flavor from esters, like acetate of terpineol, borneol, and geraniol.
Aging improves the smell and value of perfumes through esterification.
Some esters solidify at room temperature, allowing separation by cooling (e.g., benzyl benzoate).
Esters can be isolated from essential oils through shaking with dilute sulfuric acid and recrystallization with alcohol.
Fraction distillation under vacuum is needed to isolate esters, ensuring no acid is present to prevent hydrolysis.
Esters are identified through saponification, determining the corresponding acid and alcohol.

Important Esters in Volatile Oils

Aliphatic acid esters: Geranyl acetate and linalyl acetate.
Aromatic acid esters: Benzyl benzoate and methyl salicylate.
Nitrogen-containing esters: Methyl anthranilate.

Geranyl Acetate

Structure: A colorless liquid with a pleasant fruity odor.
Source: Oil of citronella, lemongrass, petit grain, lavender, and coriander.
Isolation: Fractionation distillation under vacuum.
Properties: Colorless liquid, pleasant fruity odor.
Identification: Saponify the ester. Identify geraniol and acetic acid.
Uses: Perfume, cosmetics, and food industry, natural antioxidant, to prevent cancer, antimicrobial.

Linalyl Acetate

Structure: Colorless liquid with a pleasant fruity odor, specifically of bergamot.
Source: Lavender and bergamot oils.
Isolation: Fraction distillation under vacuum (hydrolysis in atmospheric pressure).
Properties: Colorless liquid, pleasant fruity odor.
Identification: Saponify the ester. Identify linalool and acetic acid.
Uses: Perfume, antioxidant, effective antimicrobial, antispasmodic, fungicide.

Methyl Salicylate

Structure: Colorless oil with a powerful odor and flavor.
Source: Oil of wintergreen (Gaultheria procumbens).
Isolation: Enzymatic hydrolysis followed by distillation.
Properties: Colorless oil, powerful odor and flavor. FeCl3 solution creates a red-violet color.
Identification: Saponify the ester. Identify methanol and salicylic acid.
Uses: Natural substitute of Aspirin, local anti-inflammatory, antirheumatic and anticariogenic agent.

Methyl Anthranilate

Source: Oil of neroli, jasmine, and ylang ylang.
Isolation: Shaking the oil with dilute (H2SO4), ester is regenerated by NaOH.
Properties: Crystalline mass with a powerful taste, special odor, resembles orange blossoms. Has blue violet fluorescence.
Identification: Formation of derivatives (picrate needles).
Uses: Antifungal activity.

Determination of Esters

Procedure: Saponify the ester using standard alcoholic potassium hydroxide (KOH).
The amount of alkali consumed is determined by back-titrating the excess with a standardized acid.
Calculate the percentage of ester from this.

General Precautions

Some esters take longer than an hour to saponify completely (e.g., salicylates and menthyl acetate).
In dark-colored oils, dilute the saponified oil with alcohol to accurately measure the end point of titration.

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Description

Explore the fascinating world of esters and their significance in volatile oils. This quiz covers the properties, identification methods, and key esters used in flavor and aroma. Test your knowledge on how esters play a crucial role in perfumery and essential oil chemistry.