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

الاسترات هي فئة من الجزيئات العضوية التي يمكن أن يكون لها رائحة الفواكه أو المنمقة. هيكل الإستر عبارة عن كربونيل مع مجموعة ألكيل أو أريل على جانب واحد وأكسجين مرتبط بمجموعة ألكيل أو أريل أخرى على الجانب الآخر. 
اعتمادا على مجموعات الألكيل أو الأريل ، يمكن أن تأخذ الإستر العديد من الخصائص المختلفة. على سبيل المثال ، ينتج عن تفاعل الجلسرين وثلاثة أحماض دهنية ، وهي أحماض كربوكسيل ذات سلاسل ألكيل طويلة ، الدهون الثلاثية ، التي تحتوي على ثلاث مجموعات إستر. تعطي سلاسل الألكيل الطويلة من الأحماض الدهنية الدهون الثلاثية وزنا جزيئيا مرتفعا جدا. في المقابل ، فإن الاسترات البسيطة لها وزن جزيئي منخفض ومجموعات وظيفية صغيرة. 
تعزى روائح ونكهات الفواكه والزهور إلى استرات بسيطة. حتى التغييرات الصغيرة في بنية الإستر البسيط تؤثر بشكل كبير على رائحته. على سبيل المثال ، يؤدي تغيير مجموعة الهيدروكسيل إلى أمين إلى تغيير رائحة هذا الإستر من الشتاء الأخضر إلى العنب. وبالمثل ، فإن أسيتات البروبيل تنبعث منه رائحة الكمثرى ، في حين أن أسيتات البوتيل ، التي تحتوي على كربون واحد فقط في سلسلتها ، تنبعث منها رائحة التفاح. 
إحدى الطرق الشائعة لصنع إستر هي أسترة فيشر ، حيث يتفاعل حمض الكربوكسيل والكحول في وجود محفز حمضي لتشكيل الإستر والماء. تأتي المجموعة R والكربونيل من حمض الكربوكسيل ، وتأتي مجموعة الألكوكسي أو الأريلوكسي مع R من الكحول. تفاعل الأسترة هذا قابل للعكس. مع مزيج من 1 إلى 1 من حمض الكربوكسيل والكحول ، فإنه يميل إلى الوصول إلى التوازن مع حوالي 70٪ من عائد الإستر في أحسن الأحوال. 
ومع ذلك ، فإن مبدأ Le Chatelier يسمح لنا بزيادة محصول الإستر إلى ما بعد ذلك. ينص مبدأ لو شاتيلييه على أن أي نظام في حالة توازن كيميائي يخضع لتغيير في التركيز أو الضغط أو درجة الحرارة أو الحجم سوف يتكيف مع توازن جديد يقاوم التغيير. 
إذن، إذا قمنا بزيادة تركيز أحد المواد المتفاعلة في تفاعل عكسي، فسوف يتحول الاتزان في الاتجاه الذي يقلل من تركيزه. ينتج عن هذا إنتاجية أعلى من منتج الإستر في حالة توازن. وبالتالي ، يمكننا تحسين إنتاجية الأسترة باستخدام نسبة مولار 3: 1 أو 1: 3 من حمض الكربوكسيل إلى الكحول. 
في هذه التجربة ، سيتم إجراء أسترة فيشر باستخدام الكحول الزائد وحمض الكبريتيك كمحفز. في هذا التفاعل ، يتم تعزيز تفاعل حمض الكربوكسيل بواسطة حمض الكبريتيك ، الذي بروتونات أكسجين الكربونيل. الكحول عبارة عن مادة نووية تهاجم كربون الكربونيل لتشكيل وسيط. بعد ذلك ، يتم نقل هيدروجين الكحول إلى هيدروكسيل قريب. ثم يصلح الكربونيل ، مما يؤدي إلى القضاء على جزيء الماء. أخيرا ، ينتج عن إزالة البروتون إستر محايد. 
في هذا المختبر ، ستقوم بإجراء تفاعل أسترة فيشر مع كحول وحمض كربوكسيل غير معروف بنسبة مولية تبلغ 3: 1. ستحدد بعد ذلك الإستر باستخدام رائحته ، وتحدد العائد ، وتحدد الكواشف غير المعروفة بناء على بنية الإستر.

الأسترة

<h4>إسترز</h4>
هيكل الإستر عبارة عن كربونيل مع مجموعة ألكيل أو أريل (R) على جانب واحد ، وأكسجين مرتبط بمجموعة ألكيل أو أريل أخرى (R') على الجانب الآخر ، ممثلة بالصيغة العامة: RCOOR '. يمكن اشتقاق الاسترات عادة عن طريق تفاعل الأسترة بين حمض الكربوكسيل والكحول. يتم استبدال مجموعة الهيدروكسيل من حمض الكربوكسيل بمجموعة ألكيل أو أريل. الاسترات البسيطة ، التي لها وزن جزيئي منخفض ومجموعات وظيفية صغيرة R و R ، لها روائح ونكهات من الفواكه والزهور. 
أبسط حمض كربوكسيل هو حمض الفورميك (HCOOH) ، وأبسط كحول هو الميثانول. وبالتالي ، فإن أبسط إستر يتكون من أسترة هذين الجزيئين هو فورمات الميثيل (HCOOCH 3 ). يعتبر فورمات الميثيل مشتقا من حمض الفورميك لأنه يتم استبدال مجموعة OH بمجموعة OCH 3 . تملي الاختلافات الهيكلية بين فورمات الميثيل وحمض الفورميك الفرق في خصائصهما. وذلك لأن خصائص الجزيء تعتمد بشكل كبير على مجموعات R و R. 
تعرف الإسترات الموجودة في الفواكه والزهور باسم استرات بسيطة بسبب انخفاض تعقيد هيكلها بالمقارنة مع الإسترات الأخرى. تؤثر مجموعات الألكيل والأريل الموجودة في هذه الإسترات بشكل كبير على العطر الذي تنبعث منه. وبالتالي ، فإن إضافة الكربون أو مجموعة وظيفية مختلفة يمكن أن تؤثر على الرائحة التي تنتجها الإستر. على سبيل المثال ، أسيتات البروبيل (C5H10O 2) له رائحة الكمثرى. ومع ذلك ، فإن أسيتات البوتيل (C6 H 12 O 2 ) ، الذي يحتوي على كربون واحد فقط في سلسلته ، تنبعث منه رائحة التفاح. 
تسمى الإسترات طويلة السلسلة ، أي تلك التي تحتوي على سلاسل طويلة من الألكيل ، بالأحماض الدهنية. الأحماض الدهنية هي مركبات بيولوجية مهمة ضرورية لبعض العمليات البيولوجية. الأحماض الدهنية هي أيضا شكل بيولوجي لتخزين الطاقة. عندما تتفاعل ثلاثة أحماض دهنية مع الجلسرين، فإنها تشكل الدهون الثلاثية — الشكل الأكثر شيوعا للأحماض الدهنية. الدهون الثلاثية لها وزن جزيئي مرتفع جدا ويمكن أن تكون متفرعة للغاية. تعتمد وظيفتها وخصائصها على طول وأنواع سلاسل الألكيل المدمجة في هيكلها. أحد الاستخدامات الصناعية الأكثر شيوعا للدهون الثلاثية هو إنتاج الصابون والمنظفات. 
<h4>تفاعل الأسترة </h4>
تتشكل استرات من تفاعل الأسترة ، مع استرات بسيطة تتشكل من خلال الأسترة فيشر. يحول هذا التفاعل حمض الكربوكسيل والكحول إلى إستر مع الماء كمنتج ثانوي. أسترة فيشر هو تفاعل قابل للانعكاس يسير ببطء شديد. يضاف محفز حمضي ، عادة على شكل حمض الكبريتيك ، لزيادة معدل التفاعل بينما يعمل أيضا كعامل تجفيف. 
تبدأ آلية عمل أسترة فيشر بمهاجمة أكسجين الكربونيل لحمض الكبريتيك وإزالة البروتونات من مجموعة OH. هذا يؤدي إلى أكسجين كربونيل موجب الشحنة. لتحقيق الاستقرار بشكل أفضل للشحنة الموجبة ، يتم دفع زوج إلكتروني واحد من رابطة الكربونيل المزدوجة إلى أكسجين الكربونيل مع إنشاء مركز كربون فقير للإلكترون في نفس الوقت. بعد ذلك ، تعمل مجموعة الهيدروكسي من الكحول كمادة نووية وتهاجم الكربون الفقير للإلكترون - المحبة للكهرباء - مكونا وسيطا. بعد ذلك ، يتم إزالة البروتونات من مجموعة الهيدروكسيل موجبة الشحنة من الكحول بواسطة مجموعة الهيدروكسيل من حمض الكربوكسيل ، مما يؤدي إلى استقرار ذرة الأكسجين للكحول. في الخطوة الأخيرة ، يتم إزالة البروتونات من أكسجين الكربونيل بواسطة القاعدة المترافقة ، ويتم تحريك زوج الإلكترون الحر نحو مركز الكربونيل بينما تترك مجموعة الكربوكسيل البروتونية كجزيء ماء. 
نظرا لأن تفاعل الأسترة قابل للعكس ، فإن خليط 1: 1 من حمض الكربوكسيل والكحول سيصل إلى التوازن مع حوالي 70٪ من إنتاجية الإستر. ومع ذلك ، كما هو الحال مع أي عملية توازن ، يمكن دفع التفاعل في اتجاه واحد عن طريق تغيير تركيز أو ضغط أو درجة حرارة أو حجم الكواشف. يتسبب هذا التغيير في تكيف رد الفعل مع توازن جديد لمواجهة التغيير ، وهو أساس مبدأ لو شاتيلييه. 
عندما يزداد تركيز أحد المواد المتفاعلة ، يتحول التوازن في الاتجاه الذي يقلل من تركيزه. وبالتالي ، من خلال زيادة تركيز مادة متفاعلة واحدة ، ينتج التوازن المزيد من المنتج ، مما يؤدي إلى زيادة إنتاجية منتج الإستر. 
تتمثل إحدى الطرق الشائعة المستخدمة في مختبرات الكيمياء العضوية في توفير فائض من أحد الكواشف ، وعادة ما يكون الكحول. كما ذكرنا سابقا ، يمكن أن يستخدم أسترة فيشر حمض الكبريتيك كمحفز. ومع ذلك ، فإن إحدى الوظائف الأخرى لحمض الكبريتيك هي العمل كعامل تجفيف ، وعزل جزيئات الماء بعيدا عن التفاعل. يوضح تطبيق مبدأ Le Chatelier أنه عندما تتم إزالة أحد المنتجات - في هذه الحالة ، الماء - يتم دفع التفاعل لصنع المزيد من المنتجات. هذا يزيد من غلة الإستر المتكونة. 
<h4>المرجع</h4>
<ol>
	<li style="font-size:17px">Streitwieser ، A. ، Heathcock ، C.H. ، Kosower ، E.M. (1998). مقدمة في الكيمياء العضوية. نهر السرج العلوي ، نيوجيرسي: قاعة برنتيس. </li>
</ol>

استرات
هيكل الإستر عبارة عن كربونيل مع مجموعة ألكيل أو أريل (R) على جانب واحد ، وأكسجين مرتبط بمجموعة ألكيل أو أريل أخرى (R') ...

Education

JoVE Lab Manual

Chemistry

الكيمياء

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

lab techniques

Measuring with Accuracy in the Lab

Measuring with accuracy in the lab starts with careful records, the right tools, and correct reading of data. Scientists use lab notebooks to record how an experiment was done. These notes include the amounts of materials used and each step of the procedure. Without that record, an experiment cannot be repeated in the same way. Balances and glassware are used to measure solids and liquids for experiments. The precision of a measurement depends on the equipment used. Digital balances show the...

scientific measurement and lab skills

Graphs, Curve Fit, and Standard Deviation

Two-dimensional graphs help students compare an independent variable with a dependent variable in science data. In a chemistry example, temperature is the independent variable and volume is the dependent variable. After data are collected, the relationship between the two measurements must be quantified so it can be evaluated and compared with other relationships. A graph can also show when no relationship exists between the two variables. To make a two-dimensional graph, each data point needs...

stoichiometry, product yield, and limiting reactants

stoichiometry-product-yield-and-limiting-reactants

Balancing Equations and Reactant Limits

Chemical equations show how reactants change into products during a reaction. Stoichiometry is the study of the relative amounts of reactants and products. It is based on the Law of Conservation of Mass, which says matter is neither created nor destroyed. Because atoms are only rearranged, the number and identity of atoms must match on both sides of a reaction. That is why a chemical equation must be balanced. A balanced equation has the same number of atoms for each element in the reactants...

redox reactions

Oxidation States in Redox Reactions

Oxidation states help identify redox reactions. In a redox reaction, oxidation is the loss of one or more electrons, and reduction is the gain of one or more electrons. These reactions are often tracked by changes in oxidation state, also called oxidation number. Each atom in a molecule has an oxidation state. This number shows how oxidized an atom is compared with its free elemental form. It is written as the charge an atom would have if every bond were purely ionic. In that model, bonding...

ideal gas law

Gas Laws Behind the Ideal Gas Equation

The ideal gas equation brings together the main gas laws used in chemistry. Gases have molecules that are far apart, so their behavior is described with four measurable variables: pressure, volume, number of moles, and temperature. The ideal gas law links these variables with the gas constant, R, which equals 8.314 J·K−1 mol−1. Boyle’s law describes the link between pressure and volume. When temperature and the number of moles stay constant, pressure and volume change in opposite directions.

acid and base concentrations

Acids, Bases, and pH in Titration

Acids, bases, and pH explain how acidic or basic a solution is. An Arrhenius acid releases hydrogen ions when it dissolves in water, while an Arrhenius base releases hydroxide ions. These reactions also create conjugate partners: an acid forms a conjugate base after losing hydrogen, and a base forms a conjugate acid after losing hydroxyl. Every acid has a conjugate base, and every base has a conjugate acid. pH measures the amount of hydrogen ions in a solution. The pH scale runs from 0 to 14...

buffers

Buffer pH and the Common Ion Effect

Buffer solutions help keep pH steady when acids or bases are added. In water, an Arrhenius acid (HA) dissociates into hydrogen ions, H+, and a conjugate base, A-. More hydrogen ions make a solution more acidic and lower its pH. An Arrhenius base (BOH) dissociates into a conjugate acid, B+, and hydroxide ions, OH-. Strong acids and strong bases usually change pH a lot because they react completely in water and raise the amount of H+ or OH-. Buffers reduce those pH changes. A buffer usually...

enthalpy of reaction

Reaction Heat, Hess’s Law, and Calorimetry

Reaction heat is explained through enthalpy, Hess’s law, and calorimetry. These ideas show how heat moves during chemical reactions and how scientists measure it. Thermodynamics is the study of heat energy and other forms of energy, such as work. Its laws are used across science, from biology to physics. The first law says energy is conserved in an isolated system. Energy can change form, such as thermal energy becoming work, but it cannot be created or destroyed. The second law of...

solubility

Solubility in Water and Other Solvents

Solubility describes how much of a solute can dissolve in a specific solvent. It is usually reported as solute mass per solvent volume or as solute mass per solvent mass. For example, sodium chloride has a solubility of 36 g per 100 mL of water at room temperature. If solubility is given by solvent mass, that mass must be converted to volume for later calculations. Temperature changes solubility. Sodium carbonate dissolves at about 7 g per 100 mL of water at 0 °C, 22 g per 100 mL at room...

metal flame emission

Flame Test Metal Color Clues

Flame testing uses a metal sample and a flame to identify a substance by its color. Each element gives off a characteristic light emission in the flame, so the color can help distinguish one element from another. This same idea appears in fireworks, where different metal components create different colors. The color comes from energy absorbed by the metallic component. When a species absorbs energy, that energy can go into translation, vibration, rotation, or electron excitement. Electron...

balmer series

Hydrogen Emission Lines

Hydrogen emission lines show how electrons move between fixed energy levels in the Bohr model. Niels Bohr proposed this model for the hydrogen atom in 1913. In this model, an electron can only occupy certain orbits, and it cannot exist between them. These energy states are labeled with the quantum number n. The ground state is n = 1. Higher values, such as n = 2, 3, 4, and so on, are excited states. An electron changes state only by absorbing or emitting energy equal to the difference between...

beer's law

Absorbance Spectra and Beer-Lambert Analysis

Absorbance spectra and the Beer-Lambert Law show how light can be used to study molecules in solution. When light hits a substance, it may be absorbed, transmitted, or reflected. A substance often interacts with a range of wavelengths, and each wavelength can affect the molecules or atoms in a different way. When a molecule absorbs light, that energy can be used for translation, vibration, rotation, or electron excitement. Electron excitement is especially important in spectroscopy because it...

concentration dependence

Reaction Order and Rate Constants

Chemical kinetics describes the speed of a chemical reaction. The rate depends on the reaction mechanism, the complexity of the reaction, and the number of reactants involved. Reactant concentration also affects how fast a reaction happens. The rate law is the experimental relationship that connects these factors to reaction rate. In the rate law, each reactant contributes through a reaction order. The general form is r = k[A]^m[B]^n for aA + bB + ... → cC. Here, r is the reaction rate, k is...

temperature dependence

Reaction Rate, Arrhenius, and Catalysts

Chemical kinetics explains how fast a reaction happens and why that speed changes. The reaction rate is the speed of a chemical reaction. It is defined as the change in concentration of a reactant or product over time. Reaction speed depends on several factors, including the concentration of the reactants and the temperature of the reaction. Each reactant affects the rate in a specific way. That relationship is described by the rate law. The rate law is an equation that connects the...

galvanic cells

Battery Power from Redox Reactions

Electrochemistry studies how chemical change and electrical energy are linked. In this branch of chemistry, electrons move from one species to another. That movement can either produce current or be driven by an applied current. The main reaction in electrochemistry is the oxidation-reduction, or redox, reaction. A redox reaction has two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. These changes also shift the oxidation state of each substance. The...

electrolytic cells

Electroplating with Electrolytic Cells

Electrochemistry links electrical energy with chemical change, and electrolytic cells show how electricity can drive a nonspontaneous reaction. In these reactions, electrons move from one species to another. The key chemistry is a redox reaction, or oxidation-reduction reaction, which happens in two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. The substance that loses electrons is the reducing agent, and the substance that gains electrons is the...

proper lab notebook keeping

Recording a Reproducible Lab Experiment

Accurate lab notebook records are essential in science and organic chemistry labs. Without clear notes, descriptions, quantities, and observations, an experiment cannot be repeated or checked. Good record keeping supports reproducibility, which means other people can follow the same work and get similar results. A laboratory notebook is useful in school labs, research settings, and industry. It can also become a legal record when an idea, process, substance, or technique is patented and...

basic organic chemistry techniques

Organic Lab Glassware and Safe Handling

Organic chemistry labs use specific glassware, careful weighing steps, and controlled heating to keep reactions safe and accurate. Beakers and Erlenmeyer flasks are often used for mixing or holding solvents, but they are not meant for measuring volume unless only an approximate amount is needed. Volumetric glassware is used when a precise volume matters. This group includes graduated cylinders, volumetric pipettes, and volumetric flasks. A graduated cylinder is commonly used in the organic lab...

melting points

How Impurities Change Melting Points

Melting point helps identify an organic compound by showing the temperature where a solid turns into a liquid at 1 atmosphere of pressure. It is a physical property, like solubility, density, color, and electronegativity. Because the exact start of melting is hard to measure, the result is reported as a range. The lower end is when the first drops of liquid appear. The upper end is when the last solid has melted. Scientists compare this range with literature values to help identify a compound. <br...

boiling points

Boiling Point and Vapor Pressure

Boiling point and vapor pressure are key physical properties of a liquid. For a pure compound, the boiling point can help identify the substance. In experiments, the boiling point is usually recorded as a range because exact values are hard to measure and may differ by a few degrees from the literature value. Vapor pressure explains why a liquid boils. In a sealed container, some molecules at the liquid surface gain enough energy to escape into the gas phase. At the same time, some gas...

recrystallization

Purifying Crystals by Solubility

Purifying crystals by solubility is a key organic chemistry technique. Recrystallization uses differences in solubility to separate a desired solid product from starting materials, solvent, and impurities. It is one of the three standard purification methods, along with distillation and extraction. Solubility is the maximum amount of a substance that can dissolve in a fixed volume of solvent at a given temperature. Different solutes dissolve in different solvents, and their behavior can vary...

extraction

Separating Mixtures with Solvent Extraction

Solvent extraction is a common way to separate and isolate a target compound in organic chemistry. In this process, a solute moves from one phase to another so it can be separated from unreacted starting materials or impurities. Extraction is also useful when a product is dissolved in a reaction solvent that is hard to remove by evaporation, such as a solvent with a high boiling point. There are three main types of extraction. In solid-liquid extraction, the solute moves from a solid phase...

simple distillation

Separating Liquids by Boiling Point

Separating liquids by boiling point is the goal of distillation. A miscible mixture contains liquids that mix evenly, and it can be heated so that the more volatile liquid evaporates first. Volatility is a liquid’s tendency to vaporize, and boiling begins when bubbles form in the liquid phase. In a closed container, liquid and vapor can reach equilibrium, which means the rate of vaporization equals the rate of condensation. The pressure from the vapor above the liquid is called vapor pressure.

steam distillation

Steam Distillation and Low-Boiling Separation

Steam distillation is a separation method for temperature-sensitive organic compounds. It works best when the organic compound is immiscible in water, meaning the two liquids do not mix. The method helps remove the organic molecule from a non-volatile contaminant without using the higher temperatures needed for many other separations. In steam distillation, the immiscible mixture is heated until both water and the volatile organic compound distill together. The vapor rises to a condenser,...

thin-layer chromatography

TLC Separation by Polarity

Thin-layer chromatography (TLC) separates compounds in a mixture by polarity. It uses the same basic parts as other chromatography methods: a stationary phase, a mobile phase, and the solute. In TLC, the stationary phase is a thin coating on a plate instead of material packed into a column. The stationary phase in most TLC systems is polar silica gel, a form of silicon dioxide. Its surface has OH groups that can form hydrogen bonds. The sample is first spotted on a pencil start line with a...

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.

https://cloudfront.jove.com/files/banners/scicat/labbio.jpg

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

استعد لتدريس الأسترة من خلال هذا الدليل الإرشادي للمدرسين لمدة 4 دقيقة. يغطي خطوات التحضير الأساسية لمختبر Chemistry على JoVE Lab Manual.

تحضير المدرّس لـ الأسترة في Chemistry - أكثر من 10K مشاهدة | JoVE Lab Manual

اتبع إجراءات الأسترة خطوة بخطوة في فيديو بروتوكول الطالب هذا لمدة 10 دقيقة. جزء من مجموعة Chemistry على JoVE Lab Manual.

بروتوكول الطالب لـ الأسترة في Chemistry - أكثر من 20K مشاهدة | 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

Description

Transcript

More videos by Standards