Name: ester formation and everyday fragrances
Uploaded: 2020-03-26T07:22:29.000Z
Duration: 3 min 48 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Physical Science

SC.912.P.8

SC.912.P.8.13

Esterification

エステルは、フルーティーまたは花のような香りを持つことができる有機分子のクラスです。エステルの構造は、片側にアルキル基またはアリール基があり、反対側に酸素が別のアルキルまたはアリール基に結合したカルボニルです。
アルキル基またはアリール基に応じて、エステルは多くの異なる特性を帯びることができます。例えば、グリセロールと3つの脂肪酸(長いアルキル鎖を持つカルボン酸)と反応すると、3つのエステル基を持つトリグリセリドが得られます。脂肪酸からの長いアルキル鎖は、トリグリセリドに非常に高い分子量を与えます。一方、単純なエステルは分子量が低く、官能基が小さいという特徴があります。
果物や花の香りや風味は、単純なエステルに起因しています。単純なエステルの構造に小さな変化があっても、その香りには大きな影響が及びます。例えば、ヒドロキシル基をアミンに変えると、このエステルの香りがウィンターグリーンからブドウに変わります。同様に、酢酸プロピルは梨のような香りがしますが、鎖に炭素が1つしかない酢酸ブチルはリンゴのような香りがします。
エステルを作る一般的な方法の1つは、カルボン酸とアルコールが酸触媒の存在下で反応してエステルと水を形成するフィッシャーエステル化です。R基とカルボニルはカルボン酸に由来し、R'を持つアルコキシ基またはアリールオキシ基はアルコールに由来します。このエステル化反応は可逆的です。カルボン酸とアルコールを1対1で混合すると、せいぜいエステルの収率が約70%で平衡に達する傾向があります。
しかし、ル・シャトリエの原理により、それ以上にエステルの収量を増やすことができます。ル・シャトリエの原理では、濃度、圧力、温度、体積の変化にさらされた化学平衡状態のシステムは、その変化に対抗する新しい平衡に適応するというものです。
したがって、可逆反応で反応物の1つの濃度を上げると、平衡はその濃度を低下させる方向にシフトします。これにより、平衡状態でのエステル生成物の収率が高くなります。したがって、カルボン酸とアルコールの3:1または1:3のモル比を使用することで、エステル化の収率を向上させることができます。
この実験では、過剰のアルコールと触媒として硫酸を使用してフィッシャーエステル化を行います。この反応では、カルボン酸が硫酸によって反応性を高め、カルボニルの酸素をプロトン化します。アルコールは、カルボニルの炭素を攻撃して中間体を形成する求核剤です。次に、アルコールの水素は近くの水酸基に移されます。その後、カルボニルが再形成され、水分子が排除されます。最後に、脱プロトン化により中性エステルが得られます。
このラボでは、未知のアルコールとカルボン酸を用いて、モル比3:1のフィッシャーエステル化反応を行います。次に、その臭いを使用してエステルを特定し、収量を決定し、エステルの構造に基づいて2つの未知の試薬を特定します。

エステル化

<h4>エステル</h4>
エステルの構造は、片側にアルキル基またはアリール基(R)があり、反対側に酸素が別のアルキルまたはアリール基(R')に結合したカルボニルであり、一般式RCOOR'で表されます。エステルは、一般的にカルボン酸とアルコールとの間のエステル化反応によって導出されます。カルボン酸のヒドロキシル基は、アルキル基またはアリール基に置換されます。低分子量でRおよびR'官能基が小さい単純エステルは、果実や花の香りと風味を持っています。
最も単純なカルボン酸はギ酸(HCOOH)であり、最も単純なアルコールはメタノールです。したがって、これら2つの分子のエステル化から形成される最も単純なエステルは、ギ酸メチル(HCOOCH3)です。ギ酸メチルは、OH基がOCH3基に置き換わるため、ギ酸の誘導体と考えられています。ギ酸メチルとギ酸の構造的な違いが、それらの特性の違いを決定します。これは、分子の特性がR基とR'基に大きく依存するためです。
果物や花に含まれるエステルは、他のエステルに比べて構造の複雑さが低いため、単純なエステルとして知られています。これらのエステルに含まれるアルキル基とアリール基は、それらが発する香りに大きく影響します。したがって、炭素または異なる官能基の添加は、エステルによって生成される香りに影響を与える可能性があります。例えば、酢酸プロピル(C5H10O2)はナシの香りがします。しかし、酢酸ブチル(C6H12O2)は、その鎖にもう1つの炭素しか持たず、リンゴのようなにおいがします。
長鎖エステル、つまり長いアルキル鎖を持つエステルは脂肪酸と呼ばれます。脂肪酸は、特定の生物学的プロセスに不可欠な重要な生物学的化合物です。脂肪酸は、エネルギー貯蔵の生物学的形態でもあります。3つの脂肪酸がグリセロールと反応すると、脂肪酸の最も一般的な形態であるトリグリセリドが形成されます。トリグリセリドは非常に高い分子量を持ち、高度に分岐することができます。それらの機能と特性は、その構造に組み込まれたアルキル鎖の長さと種類に依存します。トリグリセリドの最も一般的な工業用途の1つは、石鹸や洗剤の製造です。
<h4>エステル化反応</h4>
エステルはエステル化反応から形成され、単純なエステルはフィッシャーエステル化によって形成されます。この反応により、カルボン酸とアルコールがエステルに変換され、副生成物として水が加わります。フィッシャーエステル化は、非常にゆっくりと進行する可逆的な反応です。酸触媒は、通常は硫酸の形で、反応速度を上げるために添加されると同時に、脱水剤としても作用します。
フィッシャーエステル化の作用機序は、カルボニル酸素が硫酸を攻撃し、そのOH基を脱プロトン化することから始まります。これにより、正に帯電したカルボニル酸素が得られます。正電荷をより安定させるために、カルボニル二重結合の1つの電子対がカルボニル酸素に押し出されると同時に、電子が乏しい炭素中心を作り出します。次に、アルコールのヒドロキシ基は求核剤として作用し、電子の少ない炭素(求電子剤)を攻撃して中間体を形成します。すると、アルコールから正に帯電したヒドロキシル基がカルボン酸のヒドロキシル基によって脱プロトン化され、アルコールの酸素原子が安定化します。最後のステップでは、カルボニル酸素が共役塩基によって脱プロトン化され、自由電子対がカルボニル中心に向かって移動し、プロトン化されたカルボキシル基が水分子として出ます。
エステル化反応は可逆的であるため、カルボン酸とアルコールの1:1の混合物は、エステルの約70%の収率で平衡に達します。ただし、他の平衡プロセスと同様に、試薬の濃度、圧力、温度、または体積を変更することで、反応を一方向に駆動できます。この変化により、反応は変化を打ち消すための新たな平衡に順応するようになり、これがル・シャトリエの原理の基礎となっています。
反応物の1つの濃度が増加すると、平衡はその濃度を低下させる方向にシフトします。したがって、1つの反応物の濃度を上げることにより、平衡は生成物をより多く生成し、それによってエステル生成物の収率が高くなります。
有機化学研究室で利用される一般的な方法の1つは、試薬の1つ(通常はアルコール)を過剰に供給することです。前述のように、フィッシャーエステル化は触媒として硫酸を利用することができます。しかし、硫酸の他の機能の1つは、脱水剤として作用し、反応から水分子を隔離することです。ル・シャトリエの原理を適用すると、生成物の1つ(この場合は水)が除去されると、反応がより多くの生成物を作ることに駆り立てられることが実証されています。これにより、形成されるエステルの収率が増加します。
<h4>参考</h4>
<ol>
	<li style="font-size:17px">Streitwieser, A., Heathcock, C.H., Kosower, E.M. (1998).有機化学入門。 ニュージャージー州アッパーサドルリバー:プレンティスホール。</li>
</ol>

エステル
エステルの構造は、片側にアルキル基またはアリール基(R)を持つカルボニルであり、別のアルキルまたはアリール基(R ')に酸素が結合しています...

Education

JoVE Lab Manual

Chemistry

化学

ester formation and everyday fragrances

Esters are organic compounds with a carbonyl group attached to an oxygen that connects to another alkyl or aryl group. Their general formula is RCOOR'. They are often made by reacting a carboxylic acid with an alcohol in an esterification reaction. In this process, the hydroxyl group of the acid is replaced by an alkyl or aryl group.

Many simple esters have familiar fruit and flower smells because their structures are small and less complex. Formic acid and methanol can combine to form methyl formate, the simplest ester from these two molecules. Methyl formate is a derivative of formic acid because the OH group is replaced by OCH3. Small changes in the R and R' groups can also change the properties and scent of an ester.

This is why similar esters can smell different. Propyl acetate has a pear-like scent, while butyl acetate smells like apples, even though the molecules differ by only one carbon. Long-chain esters are called fatty acids. They are important in biology and also serve as a form of energy storage.

When three fatty acids react with glycerol, they form a triglyceride. Triglycerides are the most common form of fatty acids and have a high molecular weight. They can also be highly branched. Their function and properties depend on the length and type of alkyl chains in their structure. Triglycerides are widely used in industry, including the production of soaps and detergents.

Simple esters are often made by Fischer esterification, which is a slow and reversible reaction. It converts a carboxylic acid and an alcohol into an ester and water. Sulfuric acid is commonly used as an acid catalyst. It speeds up the reaction and also acts as a dehydrating agent.

The reaction mechanism starts when the carbonyl oxygen interacts with sulfuric acid and becomes positively charged. The carbonyl double bond then shifts electron density toward the oxygen, leaving the carbonyl carbon more electron-poor. Next, the alcohol acts as a nucleophile and attacks that carbon, forming an intermediate. The alcohol oxygen is then deprotonated, and the carbonyl oxygen is finally deprotonated as water leaves.

Because Fischer esterification is reversible, a 1:1 mixture of the acid and alcohol reaches equilibrium at about 70% ester yield. The reaction can be pushed toward more ester by changing concentration, pressure, temperature, or volume. This follows Le Chatelier's principle, which says a system shifts to counter a change. In the lab, using excess alcohol is a common way to increase yield. Sulfuric acid also helps by removing water, and taking away this product drives the reaction to make more ester.

Ester Formation and Everyday Fragrances

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入門化学ラボコースの指導者と学生のための、包括的でカリキュラムに焦点を当てたビデオ。

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Learn how carboxylic acids and alcohols form esters, why some smell fruity, and how Fischer esterification uses sulfuric acid to boost yield.

Ester Formation and Everyday Fragrances | JoVE K12

エステル化 を教える準備を、この 4 分間の教員向けガイドで行いましょう。JoVE Lab Manual の Chemistry ラボの主要な準備手順を解説します。

Chemistry の エステル化 教員準備 - 10K+ 回の視聴 | JoVE Lab Manual

この 10 分間の学生プロトコル動画で、エステル化 の手順をステップごとに学びましょう。JoVE Lab Manual の Chemistry コレクションの一部です。

Chemistry の エステル化 学生プロトコル - 20K+ 回の視聴 | JoVE Lab Manual

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

States of Matter

Solids, liquids, and gases are the three states of matter commonly found on Earth. A solid is rigid and possesses a definite shape. A liquid flows and ...

States of Matter and Phase Changes

The internal energy of a substance&#8212;the total kinetic energy of all its molecules and the potential energy of their associated forces&#8212;depends ...

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Differentiate between physical and chemical properties and physical and chemical changes of matter.

SC.912.P.8.1

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

Phase Transitions

Whether solid, liquid, or gas, a substance&#39;s state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the ...

phase-transitions-vaporization-and-condensation

Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Vapor Pressure

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

phase-transitions-sublimation-and-deposition

Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

SC.912.P.8.2

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

The Wave Nature of Light

The nature of light has been a subject of inquiry since antiquity. In the seventeenth century, Isaac Newton performed experiments with lenses and prisms ...

The Electromagnetic Spectrum

The electromagnetic spectrum consists of all the types of electromagnetic radiation arranged according to their frequency and wavelength. Each of the ...

Interference and Diffraction

Interference is a characteristic phenomenon exhibited by waves. When two electromagnetic waves interact with their peaks and troughs coinciding, a ...

Photoelectric Effect

When light of a particular wavelength strikes a metal surface, electrons are emitted. This is called the photoelectric effect. The minimum frequency of ...

The Bohr Model

Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded ...

Emission Spectra

When solids, liquids, or condensed gases are heated sufficiently, they radiate some of the excess energy as light. Photons produced in this manner have a ...

The de Broglie Wavelength

In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a ...

The Uncertainty Principle

Werner Heisenberg considered the limits of how accurately one can measure properties of an electron or other microscopic particles. He determined that ...

The Quantum-Mechanical Model of an Atom

Shortly after de Broglie published his ideas that the electron in a hydrogen atom could be better thought of as being a circular standing wave instead of ...

Explore the scientific theory of atoms (also known as atomic theory) by describing changes in the atomic model over time and why those changes were necessitated by experimental evidence.

SC.912.P.8.3

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Ions and Ionic Charges

In ordinary chemical reactions, the nucleus &mdash; which contains the protons and neutrons of each atom and thus identifies the element &mdash; remains ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Atomic Number and Mass Number

The number of protons in the nucleus of an atom is its atomic number (Z). This is the defining trait of an element. Its value determines the identity of ...

Explore the scientific theory of atoms (also known as atomic theory) by describing the structure of atoms in terms of protons, neutrons and electrons, and differentiate among these particles in terms of their mass, electrical charges and locations within the atom.

SC.912.P.8.4

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

Electron Configurations

Electron configurations and orbital diagrams can be determined by applying the Aufbau principle (each added electron occupies the subshell of lowest ...

Electronic Structure of Atoms


An atom comprises protons and neutrons, which are contained inside the dense, central&#160;core called the nucleus, with electrons present around the ...

Electron Behavior

Electrons are negatively charged subatomic particles that are attracted to an orbit around the positively-charged nucleus of an atom. They reside in ...

Relate properties of atoms and their position in the periodic table to the arrangement of their electrons.

SC.912.P.8.5

A. A working definition of matter is that it takes up space, has mass, and has measurable properties. Matter is comprised of atomic, subatomic, and elementary particles.

B. Electrons are key to defining chemical and some physical properties, reactivity, and molecular structures. Repeating (periodic) patterns of physical and chemical properties occur among elements that define groups of elements with similar properties. The periodic table displays the repeating patterns, which are related to the atom's outermost electrons. Atoms bond with each other to form compounds.

C. In a chemical reaction, one or more reactants are transformed into one or more new products. Many factors shape the nature of products and the rates of reaction. 

D. Carbon-based compounds are building-blocks of known life forms on earth and numerous useful natural and synthetic products.

Ester Formation and Everyday Fragrances

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