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

Esterler, meyveli veya çiçekli bir aromaya sahip olabilen bir organik molekül sınıfıdır. Bir esterin yapısı, bir tarafında bir alkil veya aril grubu ve diğer tarafında başka bir alkil veya aril grubuna bağlı bir oksijen bulunan bir karbonildir.
Alkil veya aril gruplarına bağlı olarak, ester birçok farklı özellik alabilir. Örneğin, karboksilik asitler olan gliserol ve üç yağ asidinin uzun alkil zincirleri ile reaksiyonu, üç ester grubuna sahip bir trigliserit ile sonuçlanır. Yağ asitlerinden gelen uzun alkil zincirleri, trigliseritlere çok yüksek bir moleküler ağırlık verir. Buna karşılık, basit esterler düşük moleküler ağırlığa ve küçük fonksiyonel gruplara sahiptir.
Meyve ve çiçeklerin kokuları ve tatları basit esterlere atfedilir. Basit bir esterin yapısındaki küçük değişiklikler bile kokusunu büyük ölçüde etkiler. Örneğin, bir hidroksil grubunu bir amine dönüştürmek, bu esterin kokusunu kış yeşilinden üzüme değiştirir. Benzer şekilde, propil asetat armut gibi kokarken, zincirinde sadece bir karbon daha bulunan butil asetat elma gibi kokar.
Bir ester yapmanın yaygın bir yolu, bir karboksilik asit ve bir alkolün, ester ve suyu oluşturmak için bir asit katalizörü varlığında reaksiyona girdiği Fischer esterifikasyonudur. R grubu ve karbonil, karboksilik asitten gelir ve R' ile alkoksi veya ariloksi grubu alkolden gelir. Bu esterleşme reaksiyonu tersine çevrilebilir. 1'e 1 karboksilik asit ve alkol karışımı ile, en iyi ihtimalle yaklaşık% 70'lik bir ester verimi ile dengeye ulaşma eğilimindedir.
Bununla birlikte, Le Chatelier'in prensibi, esterin verimini bunun ötesine çıkarmamıza izin verir. Le Chatelier ilkesi, konsantrasyon, basınç, sıcaklık veya hacimde bir değişikliğe maruz kalan kimyasal dengedeki herhangi bir sistemin, değişime karşı koyan yeni bir dengeye uyum sağlayacağını belirtir.
Dolayısıyla, tersinir bir reaksiyonda reaktanlardan birinin konsantrasyonunu arttırırsak, denge konsantrasyonunu azaltan yönde kayacaktır. Bu, dengede ester ürününün daha yüksek bir verimi ile sonuçlanır. Böylece, karboksilik asidin alkole 3:1 veya 1:3 molar oranını kullanarak esterleştirme verimini artırabiliriz.
Bu deneyde, fazla alkol ve katalizör olarak sülfürik asit kullanılarak bir Fischer esterifikasyonu gerçekleştirilecektir. Bu reaksiyonda, karboksilik asit reaktivitesi, karbonilin oksijenini protonlayan sülfürik asit ile arttırılır. Alkol, bir ara ürün oluşturmak için karbonilin karbonuna saldıran bir nükleofildir. Daha sonra, alkolün hidrojeni yakındaki bir hidroksil'e aktarılır. Karbonil daha sonra yeniden şekillenir ve bir su molekülünü ortadan kaldırır. Son olarak, protondan arındırma nötr bir ester ile sonuçlanır.
Bu laboratuvarda, bilinmeyen bir alkol ve karboksilik asit ile 3:1 molar oranında bir Fischer esterleştirme reaksiyonu gerçekleştireceksiniz. Daha sonra kokusunu kullanarak esteri tanımlayacak, verimi belirleyecek ve esterin yapısına göre bilinmeyen iki reaktifi tanımlayacaksınız.

esterleşme

<h4>Ester</h4>
Bir esterin yapısı, bir tarafında bir alkil veya aril grubu (R) bulunan bir karbonil ve diğer tarafında başka bir alkil veya aril grubuna (R') bağlı bir oksijendir ve genel formülle temsil edilir: RCOOR'. Esterler yaygın olarak bir karboksilik asit ile bir alkol arasındaki bir esterleştirme reaksiyonu ile türetilebilir. Karboksilik asidin hidroksil grubu, bir alkil veya aril grubu ile değiştirilir. Düşük molekül ağırlığına ve küçük R ve R' fonksiyonel gruplarına sahip olan basit esterler, meyve ve çiçeklerin koku ve tatlarına sahiptir.
En basit karboksilik asit formik asittir (HCOOH), en basit alkol ise metanoldür. Bu nedenle, bu iki molekülün esterleşmesinden oluşan en basit ester metil formattır (HCOOCH3). Metil format, formik asidin bir türevi olarak kabul edilir, çünkü OH grubuOCH3 grubu ile değiştirilir. Metil format ve formik asit arasındaki yapısal farklılıklar, özelliklerindeki farkı belirler. Bunun nedeni, molekülün özelliklerinin büyük ölçüde R ve R' gruplarına bağlı olmasıdır.
Meyvelerde ve çiçeklerde bulunan esterler, diğer esterlere kıyasla yapılarının düşük karmaşıklığı nedeniyle basit esterler olarak bilinir. Bu esterlerde bulunan alkil ve aril grupları, yaydıkları kokuyu büyük ölçüde etkiler; Bu nedenle, bir karbon veya farklı bir fonksiyonel grubun eklenmesi, ester tarafından üretilen kokuyu etkileyebilir. Örneğin, propil asetat (C5H10O2) armut kokusuna sahiptir. Bununla birlikte, zincirinde sadece bir karbon daha bulunan butil asetat (C6H12O2) elma gibi kokar.
Uzun zincirli esterler, yani uzun alkil zincirlerine sahip olanlara yağ asitleri denir. Yağ asitleri, belirli biyolojik süreçler için gerekli olan önemli biyolojik bileşiklerdir. Yağ asitleri aynı zamanda biyolojik bir enerji depolama şeklidir. Üç yağ asidi gliserol ile reaksiyona girdiğinde, yağ asitlerinin en yaygın şekli olan bir trigliserit oluştururlar. Trigliseritler çok yüksek bir moleküler ağırlığa sahiptir ve oldukça dallı olabilir. İşlevleri ve özellikleri, yapılarına dahil edilen alkil zincirlerinin uzunluğuna ve türlerine bağlıdır. Trigliseritlerin en yaygın endüstriyel kullanımlarından biri sabun ve deterjan üretimidir.
<h4>Esterleşme Reaksiyonu</h4>
Esterler, bir esterleştirme reaksiyonundan oluşur ve basit esterler, Fisher esterifikasyonu yoluyla oluşturulur. Bu reaksiyon, bir karboksilik asit ve alkolü, yan ürün olarak su ile bir estere dönüştürür. Fisher esterleşmesi, çok yavaş ilerleyen tersinir bir reaksiyondur. Tipik olarak sülfürik asit formunda bir asit katalizörü, reaksiyonun hızını artırmak ve aynı zamanda bir dehidrasyon maddesi olarak işlev görmek için eklenir.
Bir Fisher esterifikasyonu için etki mekanizması, karbonil oksijenin sülfürik aside saldırması ve OH grubunu protondan arındırmasıyla başlar. Bu, pozitif yüklü bir karbonil oksijene yol açar. Pozitif yükü daha iyi stabilize etmek için, karbonil çift bağının bir elektron çifti karbonil oksijene itilirken aynı anda elektron bakımından fakir bir karbon merkezi oluşturulur. Daha sonra, alkolün hidroksi grubu bir nükleofil görevi görür ve elektron bakımından fakir karbona - elektrofil - saldırır ve bir ara madde oluşturur. Daha sonra, alkolden gelen pozitif yüklü hidroksil grubu, karboksilik asidin hidroksil grubu tarafından protondan arındırılır ve alkolün oksijen atomunu stabilize eder. Son adımda, karbonil oksijen, konjuge baz tarafından protondan arındırılır ve protonlanmış karboksil grubu bir su molekülü olarak ayrılırken serbest elektron çifti karbonil merkezine doğru hareket ettirilir.
Esterleştirme reaksiyonu geri dönüşümlü olduğundan, karboksilik asit ve alkolün 1:1 karışımı, esterin yaklaşık %70 verimi ile dengeye ulaşacaktır. Bununla birlikte, herhangi bir denge işleminde olduğu gibi, reaktiflerin konsantrasyonu, basıncı, sıcaklığı veya hacmi değiştirilerek reaksiyon bir yönde sürülebilir. Bu değişim, Le Chatelier ilkesinin temeli olan değişime karşı koymak için reaksiyonun yeni bir dengeye uyum sağlamasına neden olur.
Reaktanlardan birinin konsantrasyonu arttığında, denge, konsantrasyonunu azaltacak yönde kayar. Böylece, bir reaktantın konsantrasyonunu artırarak, denge daha fazla ürün üretir, böylece ester ürününün daha yüksek bir verimi ile sonuçlanır.
Organik kimya laboratuvarlarında kullanılan yaygın bir yöntem, reaktiflerden birinin, tipik olarak alkolün fazla miktarda sağlanmasıdır. Daha önce de belirtildiği gibi, Fisher esterifikasyonu sülfürik asidi bir katalizör olarak kullanabilir. Bununla birlikte, sülfürik asidin diğer işlevlerinden biri, su moleküllerini reaksiyondan uzaklaştıran bir dehidrasyon maddesi olarak hareket etmektir. Le Chatelier'in prensibini uygulamak, ürünlerden biri çıkarıldığında - bu durumda su - reaksiyonun daha fazla ürün yapmaya itildiğini gösterir. Bu, oluşan esterin verimini arttırır.
<h4>referans</h4>
<ol>
	<li style="font-size:17px">Streitwieser, A., Heathcock, C.H., Kosower, E.M. (1998). Organik Kimyaya Giriş. Yukarı Saddle Nehri, NJ: Prentice Salonu.</li>
</ol>

Esterleşme

Ester
Bir esterin yapısı, bir tarafında bir alkil veya aril grubu (R) olan bir karbonil ve başka bir alkil veya aril grubuna (R') bağlı bir oksijendir ...

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JoVE Lab Manual

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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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Kimya laboratuvar temelleri için, hem eğitmenlere hem de öğrencilere yönelik, kapsamlı ve müfredat odaklı vidolar.

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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

Esterleşme öğretimine bu 4 dakikalık eğitmen rehberiyle hazırlanın. JoVE Lab Manual üzerindeki Chemistry laboratuvarı için temel hazırlık adımlarını kapsar.

Chemistry içinde Esterleşme Eğitmen Hazırlığı - 10K+ Görüntülenme | JoVE Lab Manual

10 dakikalık bu öğrenci protokol videosunda Esterleşme prosedürlerini adım adım takip edin. JoVE Lab Manual üzerindeki Chemistry koleksiyonunun bir parçasıdır.

Chemistry içinde Esterleşme Öğrenci Protokolü - 20K+ Görüntülenme | 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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