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

Сложные эфиры — это класс органических молекул, которые могут иметь фруктовый или цветочный аромат. Структура сложного эфира представляет собой карбонил с алкильной или арильной группой с одной стороны и кислородом, связанным с другой алкильной или арильной группой с другой стороны.
В зависимости от алкильных или арильных групп сложный эфир может принимать множество различных характеристик. Например, реакция глицерина и трех жирных кислот, которые являются карбоновыми кислотами с длинными алкильными цепями, приводит к образованию триглицерида, который имеет три эфирные группы. Длинные алкильные цепи жирных кислот придают триглицеридам очень высокую молекулярную массу. В отличие от них, простые сложные эфиры имеют низкую молекулярную массу и небольшие функциональные группы.
Запахи и вкусы фруктов и цветов относят к простым эфирам. Даже небольшие изменения в структуре простого эфира сильно влияют на его аромат. Например, изменение гидроксильной группы на амин меняет запах этого эфира с грушанки на виноградную. Точно так же пропилацетат пахнет грушами, в то время как бутилацетат, который имеет в своей цепочке всего на один атом углерода больше, пахнет яблоками.
Одним из распространенных способов получения сложного эфира является этерификация по Фишеру, при которой карбоновая кислота и спирт вступают в реакцию в присутствии кислотного катализатора с образованием эфира и воды. R группа и карбониль происходят из карбоновой кислоты, а алкокси или арилоксигруппа с R' — из алкоголя. Эта реакция этерификации обратима. При соотношении 1 к 1 смеси карбоновой кислоты и спирта он стремится достичь равновесия с выходом эфира в лучшем случае около 70%.
Тем не менее, принцип Ле Шателье позволяет нам увеличить выход эфира сверх этого. Принцип Ле Шателье гласит, что любая система, находящаяся в химическом равновесии, которая подвергается изменению концентрации, давления, температуры или объема, приспособится к новому равновесию, которое противодействует этому изменению.
Таким образом, если мы увеличим концентрацию одного из реагентов в обратимой реакции, равновесие сместится в сторону, которая уменьшит его концентрацию. Это приводит к более высокому выходу эфирного продукта в равновесном состоянии. Таким образом, мы можем улучшить выход этерификации, используя молярное соотношение карбоновой кислоты и спирта 3:1 или 1:3.
В этом эксперименте будет выполнена этерификация по Фишеру с использованием избыточного спирта и серной кислоты в качестве катализатора. В этой реакции реакционная способность карбоновой кислоты усиливается серной кислотой, которая протонирует кислород карбонила. Алкоголь является нуклеофилом, который атакует углерод карбонила с образованием промежуточного продукта. Затем водород спирта переносится в соседний гидроксил. Затем карбонил преобразуется, уничтожая молекулу воды. Наконец, депротонирование приводит к образованию нейтрального эфира.
В этой лаборатории вы проведете реакцию этерификации Фишера с неизвестным спиртом и карбоновой кислотой в молярном соотношении 3:1. Затем вы определите сложный эфир по его запаху, определите выход и определите два неизвестных реагента на основе структуры эфира.

Этерификации

<h4>Эфиры</h4>
Структура сложного эфира представляет собой карбонил с алкильной или арильной группой (R) с одной стороны и кислородом, связанным с другой алкильной или арильной группой (R') с другой стороны, представленный общей формулой: RCOOR'. Сложные эфиры обычно могут быть получены в результате реакции этерификации между карбоновой кислотой и спиртом. Гидроксильная группа карбоновой кислоты заменяется алкильной или арильной группой. Простые сложные эфиры, которые имеют низкую молекулярную массу и малые функциональные группы R и R', имеют запахи и вкус фруктов и цветов.
Самой простой карбоновой кислотой является муравьиная кислота (HCOOH), а самым простым спиртом является метанол. Таким образом, простейшим эфиром, образующимся в результате этерификации этих двух молекул, является метилформиат (HCOOCH3). Метилформиат считается производным муравьиной кислоты, потому что группа OH заменена на группу OCH3. Структурные различия между метилформиатом и муравьиной кислотой обуславливают разницу в их свойствах. Это связано с тем, что свойства молекулы сильно зависят от R- и R'-групп.
Сложные эфиры, которые содержатся во фруктах и цветах, известны как простые сложные эфиры из-за низкой сложности их структуры по сравнению с другими сложными эфирами. Алкильные и арильные группы, содержащиеся в этих эфирах, сильно влияют на аромат, который они издают; Таким образом, добавление углерода или другой функциональной группы может повлиять на запах, производимый эфиром. Например, пропилацетат (C5H10O2) имеет аромат груш. Однако бутилацетат (C6H12O2), который имеет в своей цепочке всего на один углерод больше, пахнет яблоками.
Длинноцепочечные эфиры, то есть те, которые имеют длинные алкильные цепи, называются жирными кислотами. Жирные кислоты являются важными биологическими соединениями, которые необходимы для определенных биологических процессов. Жирные кислоты также являются биологической формой хранения энергии. Когда три жирные кислоты вступают в реакцию с глицерином, они образуют триглицерид — наиболее распространенную форму жирных кислот. Триглицериды имеют очень высокую молекулярную массу и могут быть сильно разветвленными. Их функция и свойства зависят от длины и типа алкильных цепей, входящих в их структуру. Одним из наиболее распространенных промышленных применений триглицеридов является производство мыла и моющих средств.
<h4>Реакция этерификации</h4>
Сложные эфиры образуются в результате реакции этерификации, а простые сложные эфиры образуются в результате этерификации по Фишеру. Эта реакция превращает карбоновую кислоту и спирт в сложный эфир с водой в качестве побочного продукта. Этерификация по Фишеру – это обратимая реакция, протекающая очень медленно. Кислотный катализатор, обычно в форме серной кислоты, добавляется для увеличения скорости реакции, а также действует как дегидратирующий агент.
Механизм действия для этерификации по Фишеру начинается с того, что карбонильный кислород атакует серную кислоту и депротонирует ее группу ОН. Это приводит к положительно заряженному карбонильному кислороду. Чтобы лучше стабилизировать положительный заряд, одна электронная пара карбонильной двойной связи подталкивается к карбонильному кислороду, одновременно создавая бедный электронами углеродный центр. Далее, гидроксигруппа алкоголя действует как нуклеофил и атакует бедный электронами углерод — электрофил — образуя промежуточный продукт. Затем положительно заряженная гидроксильная группа из алкоголя депротонируется гидроксильной группой карбоновой кислоты, стабилизируя атом кислорода алкоголя. На последнем этапе карбонильный кислород депротонируется сопряженным основанием, и пара свободных электронов перемещается к карбонильному центру, в то время как протонированная карбоксильная группа покидает его в виде молекулы воды.
Поскольку реакция этерификации является обратимой, смесь карбоновой кислоты и спирта в соотношении 1:1 достигнет равновесия с выходом эфира около 70%. Однако, как и в любом равновесном процессе, реакция может протекать в одном направлении путем изменения концентрации, давления, температуры или объема реагентов. Это изменение заставляет реакцию приспосабливаться к новому равновесию, чтобы противодействовать изменению, что является основой принципа Ле Шателье.
Когда концентрация одного из реагентов увеличивается, равновесие смещается в сторону, которая приводит к уменьшению его концентрации. Таким образом, при увеличении концентрации одного реагента равновесие производит больше продукта, что приводит к более высокому выходу эфирного продукта.
Одним из распространенных методов, используемых в лабораториях органической химии, является получение избытка одного из реагентов, обычно спирта. Как упоминалось ранее, этерификация по Фишеру может использовать серную кислоту в качестве катализатора. Тем не менее, одна из других функций серной кислоты заключается в том, чтобы действовать как дегидратирующий агент, изолируя молекулы воды от реакции. Применение принципа Ле Шателье показывает, что при удалении одного из продуктов — в данном случае воды — реакция подталкивается к получению большего количества продукта. Это увеличивает выход образующегося эфира.
<h4>ссылка</h4>
<ol>
	<li style="font-size:17px">Streitwieser, A., Heathcock, C.H., Kosower, E.M. (1998). Введение в органическую химию. Аппер Сэддл Ривер, Нью-Джерси: Прентис Холл.</li>
</ol>

Эфиры
Структура сложного эфира представляет собой карбонил с алкильной или арильной группой (R) с одной стороны и кислородом, связанным с другой алкильной или арильной группой (R') ...

Education

JoVE Lab Manual

Chemistry

Химия

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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column chromatography

Separating Mixtures by Polarity

Column chromatography separates compounds in an organic chemistry lab by using differences in physical properties. It is especially useful for microscale separations when less than 10 grams of material is available for analysis. The method can separate a mixture based on solubility, polarity, hydrophobicity, size, and charge. Any chromatography system has three main parts: the stationary phase, the mobile phase, and the sample mixture. In column chromatography, the stationary phase is usually...

hydrolysis of an ester

Soap Formation from Triglycerides

Triglycerides are lipids made of a glycerol backbone linked to three fatty acids. They are common in vegetable oils and animal fats. Plant lipids are the basis of vegetable oils, while animal lipids are used as lard or general sources of fats. A fatty acid has a long carbon chain, usually between 12 and 20 carbons, with a weak organic acid at one end. Some fatty acids contain double bonds. These are unsaturated fats. The double bond usually gives the chain a bent, cis shape. As a result,...

synthesis of luminol

Luminol Chemiluminescence in Forensics

Luminol chemiluminescence shows how a chemical reaction can produce light and help with blood detection. Chemical reactions may be endothermic or exothermic, depending on whether they absorb or release heat as reactants become products. The enthalpy of a reaction is the energy difference between reactants and products, or ΔH. A positive ΔH means the reaction is endothermic. A negative ΔH means it is exothermic. Many reactions do not happen in a single step. They can pass through intermediates...

esterification

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...

identification of unknown aldehydes and ketones

identification-of-unknown-aldehydes-and-ketones

Carbonyl Tests for Aldehydes and Ketones

Aldehydes and ketones are carbonyl compounds, which means they contain a C=O functional group. A ketone has two alkyl or aryl groups attached to the carbonyl carbon. Acetone is the simplest ketone, with two methyl groups. An aldehyde is similar, but it has at least one hydrogen attached to the carbonyl carbon. Formaldehyde is the simplest aldehyde, and acetaldehyde has one hydrogen and one methyl group. The carbonyl carbon in both aldehydes and ketones is electrophilic because the oxygen atom...

uv-vis spectroscopy of dyes

How Dyes Absorb Visible Light

Dyes absorb visible light because their molecular structure lets them interact with specific wavelengths. When light hits a substance, some light is absorbed and the rest is reflected or transmitted. The color we see depends on the wavelength that is reflected. A blue substance reflects blue light, around 430 to 480 nm, and absorbs the complementary orange region, around 590 to 630 nm. Compounds that do not absorb in the visible range appear colorless to the human eye. Light also has energy and...

identifying alcohols

Alcohol Tests for Primary, Secondary, and Tertiary

Alcohol tests can help sort alcohols by structure and reactivity. Alcohols are organic molecules with a hydroxyl group attached to an alkyl or aryl group, written as ROH. If the carbon with the hydroxyl group has one R group, the alcohol is primary. If it has two R groups, it is secondary. If it has three R groups, it is tertiary. Alcohols can also be aromatic when they contain a benzene ring. Phenol is the simplest aromatic alcohol. To identify an alcohol, chemists can use its chemical...

chemistry

Comprehensive, curriculum-focused videos for both instructors and students in introductory chemistry lab courses.

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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

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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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