Name: separating mixtures with solvent extraction
Uploaded: 2020-03-26T07:22:28.000Z
Duration: 2 min 55 s
Channel: JoVE

L’extraction est une technique permettant de séparer les composants d’un mélange. Vous êtes déjà familier avec l’extraction. Chaque fois que vous infusez du thé, vous extrayez des composés hydrosolubles, comme la caféine et les arômes, des feuilles de thé dans votre eau chaude. Il s’agit d’un exemple d’extraction solide-liquide.
L’extraction liquide-liquide est un autre type d’extraction où le mélange est dissous en deux phases liquides non miscibles. Les solvants doivent être non miscibles, c’est-à-dire qu’ils ne se mélangent pas et qu’il s’agit de phases distinctes. Les extractions liquide-liquide sont effectuées dans un entonnoir séparateur de sorte que le solvant le plus dense se dépose au fond et que le solvant le moins dense se trouve sur le dessus. Ensuite, chaque composé soluté sera transféré dans la phase dans laquelle il est le plus soluble. Par conséquent, il est important de choisir des solvants de polarités différentes.
En général, les solutés non polaires se répartissent dans la phase organique, et les solutés polaires se répartissent dans la phase aqueuse. Le coefficient de partage, K, est le rapport entre la concentration de soluté dans la phase organique et celle dans la phase aqueuse. Une fois que les solutés se sont séparés, les deux phases différentes sont collectées. Gardez à l’esprit qu’il est probable qu’il y aura des résidus de chaque composant dans les deux phases.
Une extraction acide-base est un type spécial d’extraction liquide-liquide qui sépare les composés acides et basiques en fonction des différences de solubilité. Rappelons qu’un acide est un composé qui donne un proton lorsqu’il est dissous dans l’eau, et qu’une base est un composé qui accepte un proton.
Pour séparer les composés acides, une base est ajoutée au mélange. La base acceptera un proton du composé acide, ce qui le rendra ionique. À l’inverse, l’ajout d’un acide transférerait un proton à un composé basique. Dans les deux cas, le composé ionique sera transféré dans la phase aqueuse et les composés neutres se répartiront dans la phase organique. Le composé ionique est collecté, puis déprotoné ou reprotoné pour le reconvertir en son composé d’origine.
Dans ce laboratoire, vous séparerez un mélange de cellulose, d’acide benzoïque et de caféine. Tout d’abord, vous utiliserez l’extraction et la filtration pour isoler la cellulose. Ensuite, vous effectuerez une extraction acido-basique pour séparer l’acide benzoïque et la caféine.

extraction

extraction
L’extraction est une technique couramment utilisée en chimie organique pour isoler un composé cible. Dans le processus d’extraction, un soluté est transféré d’une phase à une autre pour le séparer des matériaux de départ ou des impuretés n’ayant pas réagi. L’extraction est également utilisée pour faciliter l’isolement d’un soluté à partir d’un solvant réactionnel difficile à éliminer par évaporation, tel qu’un solvant à point d’ébullition élevé.<span style="color : rgb(0, 0, 0) ; famille de polices : Roboto, RobotoDraft, Helvetica, Arial, sans-serif ; taille de la police : 13px ; font-style : normal ; font-variant-ligatures : normal ; font-variant-caps : normal ; poids de la police : 400 ; espacement des lettres : normal ; orphelins : 2 ; text-align : démarrer ; retrait_texte : 0px ; transformation_texte : aucun ; espace blanc : pré-emballage ; veuves : 2 ; espacement des mots : 0px ; -webkit-text-stroke-width : 0px ; couleur d’arrière-plan : RGB(255, 255, 255) ; style-de-décoration-de-texte : initial ; text-decoration-color : initial ; display : inline !important ; flottant : aucun ; > Généralement, il existe trois types d’extractions. Tout d’abord, dans l’extraction solide-liquide, le soluté est transféré d’une phase solide à une phase liquide. Dans l’extraction liquide-liquide, un soluté est transféré d’un liquide à un autre. Dans l’extraction acide-base, un soluté est transformé en un composé ionique et transféré d’une phase organique à une phase aqueuse. Un exemple courant d’extraction est l’infusion du café ou du thé. La phase solide, qui contient la caféine, les arômes et les odeurs des plantes, est extraite par l’eau chaude dans la phase liquide.
Extraction liquide-liquide
Une extraction liquide-liquide transfère soit un composé organique dissous dans une phase aqueuse à un solvant organique, soit elle est utilisée pour transférer des réactifs, des sels et d’autres impuretés hydrosolubles n’ayant pas réagi à la phase aqueuse tout en laissant le composé organique d’intérêt dans la phase organique. Les liquides non miscibles sont des liquides qui ne forment jamais une solution homogène, même lorsqu’ils sont bien mélangés. Au lieu de cela, les liquides non miscibles se séparent en différentes phases, comme l’huile et l’eau.
Une extraction liquide-liquide transfère un composé organique dissous en phase aqueuse à un solvant organique. Pour effectuer une extraction liquide-liquide, la solution aqueuse contenant le soluté est d’abord ajoutée à un entonnoir séparateur. Ensuite, un solvant organique non soluble dans l’eau est ajouté à l’entonnoir séparateur. Lorsque le contenu de l’entonnoir est bien mélangé, le composé organique se répartit dans la phase organique en raison de sa solubilité plus élevée dans la phase organique que dans la phase aqueuse.
Comme les deux solvants sont non miscibles, les deux liquides forment des couches discrètes, avec le liquide dense en bas et le liquide moins dense en haut. Une fois que les deux phases se sont stabilisées en deux couches, elles sont séparées en ouvrant le robinet d’arrêt au fond de l’entonnoir de séparation et en permettant à une couche de s’écouler. Le liquide qui a été éliminé s’appelle le raffinat, tandis que le liquide qui a obtenu le soluté est appelé l’extrait.
Le composé organique est réparti entre les deux couches en fonction de sa solubilité dans chaque phase. L’équilibre est atteint lorsque le potentiel chimique du soluté est le même dans les deux phases. Le coefficient de partage d’un soluté, K, est le rapport entre la concentration de l’échantillon dans la couche organique divisée par la concentration dans la phase aqueuse. Le coefficient de partage est une constante qui dépend à la fois du soluté et de la paire de solvants utilisés dans l’extraction. Le coefficient de partage est l’expression de la préférence du soluté pour chacun des deux solvants. Les solutés avec un coefficient de partage élevé ont une plus grande tendance à être extraits dans la couche de solvant organique. Les solutés à faible coefficient de partage préfèrent passer à la phase aqueuse.
Déterminer quelle paire de solvants utiliser pour une extraction liquide-liquide est une étape essentielle. Tenez compte de ce qui suit lorsque vous choisissez les solvants à utiliser : Tout d’abord, le soluté doit être plus soluble dans le solvant que dans l’eau. Par conséquent, il est nécessaire de connaître le coefficient de partage du soluté dans une paire de solvants potentiels. Deuxièmement, la paire de solvants doit être non miscible dans l’eau et ne pas former une solution homogène lorsqu’elle est mélangée. Troisièmement, les solvants doivent être inertes et ne pas réagir avec le soluté. Le solvant doit également être volatil afin de pouvoir être facilement éliminé du soluté. Le solvant organique non miscible à l’eau possède généralement une polarité non polaire ou faible.
Il est également essentiel de connaître les densités des solvants pour déterminer l’identité des couches supérieure et inférieure. La plupart des liquides organiques ont une densité inférieure à celle de l’eau, à l’exception des solvants organiques chlorés, et se déposent au fond de l’entonnoir de séparation.
Extraction acide-base
L’extraction acide-base est un type d’extraction liquide-liquide qui sépare les composés organiques en fonction de leurs propriétés acido-basiques. Si un soluté est un acide ou une base, sa charge change en même temps que le pH. En général, la plupart des composés organiques sont neutres et donc plus solubles dans les solvants organiques que dans l’eau. Cependant, si le composé organique devient ionique, il devient plus soluble dans l’eau. Ceci est utile pour extraire un acide organique ou un composé de base d’une phase organique à une phase aqueuse.
L’extraction acide-base exploite cette propriété en transformant le soluté en sa forme de sel soluble dans l’eau, modifiant ainsi sa solubilité. La solubilité du composé organique et de son sel doit être radicalement différente pour que la technique soit efficace.
Par exemple, considérons un mélange contenant un acide carboxylique organique, une amine et un composé neutre. Les acides carboxyliques constitués de six carbones ou plus sont insolubles dans l’eau et entièrement solubles dans les solvants organiques. Cependant, leurs bases conjuguées (un composé ionique) sont solubles dans l’eau et insolubles dans les solvants organiques. Une amine composée d’au moins sept carbones est insoluble dans l’eau mais soluble dans les solvants organiques. L’acide conjugué de cette amine (un composé ionique) est soluble dans l’eau et insoluble dans les solvants organiques.
Lorsqu’il réagit avec une base, l’acide carboxylique est neutralisé sous sa forme saline. Les autres composés du mélange restent neutres. Une fois que l’acide carboxylique est transformé en sel, il va se répartir dans la phase aqueuse, tandis que les composés neutres restent dans la phase organique.
L’extraction acide-base est également utilisée pour séparer deux acides faibles ou deux bases faibles avec une différence significative dans leur pKa. Dans le cas des acides, l’acide relativement plus fort, ayant une faible valeur pKa, est neutralisé en un sel à l’aide d’une base faible. La base faible ne réagit pas efficacement avec l’acide plus faible, et seul l’acide le plus fort se transforme en sel. Ensuite, le sel est extrait dans la phase aqueuse lors de l’extraction. Le processus se déroule de la même manière pour les bases faibles, où la base relativement plus forte est neutralisée en un sel à l’aide d’un acide faible.
références
<ol>
	<li style="font-size :17px">Harris, D.C. (2015). Analyse chimique quantitative. New York, NY : W.H. Freeman et compagnie.</li>
</ol>

Extraction

Extraction
L’extraction est une technique couramment utilisée en chimie organique pour isoler un composé cible. Dans le processus d’extraction, un soluté est transféré ...

Education

Enseignement

JoVE Lab Manual

Chemistry

Chimie

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 into a liquid phase. In liquid-liquid extraction, the solute moves from one liquid into another. In acid-base extraction, the solute is changed into an ionic compound and moved from an organic phase into an aqueous phase. A familiar example is brewing coffee or tea, where hot water extracts caffeine, plant flavors, and odors from the solid material.

Liquid-liquid extraction is used when an organic compound is dissolved in water or when water-soluble impurities need to be removed from an organic product. It works with immiscible liquids, which are liquids that do not form one uniform solution, even after mixing. Oil and water are a common example. To carry out this extraction, the aqueous solution is placed in a separatory funnel, and a non-water-soluble organic solvent is added. After mixing, the compound partitions into the phase where it is more soluble.

Because the two liquids are immiscible, they separate into layers after settling. The denser liquid forms the bottom layer, and the less dense liquid stays on top. The layers are then separated by opening the stopcock at the bottom of the separatory funnel and letting one layer drain out. The layer that loses the solute is called the raffinate, and the layer that gains the solute is called the extract. At equilibrium, the solute has the same chemical potential in both phases.

The partition coefficient, K, describes how a solute divides between the two layers. It is the concentration in the organic layer divided by the concentration in the aqueous layer. This value depends on the solute and the solvent pair used. A large partition coefficient means the solute prefers the organic layer. A small partition coefficient means the solute prefers the aqueous layer. Choosing the right solvent pair is important, so the solute should be more soluble in that solvent than in water, the two solvents should be immiscible, and the solvents should be inert and volatile. The water-immiscible organic solvent is usually non-polar or low in polarity.

Knowing density is also important because it tells which layer is on top and which is on the bottom. Most organic liquids are less dense than water and rise to the top, although chlorinated organic solvents are an exception and can settle to the bottom. Acid-base extraction is a special type of liquid-liquid extraction that separates organic compounds based on acid-base behavior. When pH changes, the charge on an acid or base can change too. Neutral organic compounds are usually more soluble in organic solvents, but ionic forms are more soluble in water.

This property lets chemists turn an organic acid or base into a water-soluble salt. The salt and the neutral compound must have very different solubilities for the method to work well. For example, a mixture may contain an organic carboxylic acid, an amine, and a neutral compound. Carboxylic acids with six carbons or more are insoluble in water and soluble in organic solvents, but their conjugate bases are water-soluble and insoluble in organic solvents. Amines with at least seven carbons are insoluble in water and soluble in organic solvents, while their conjugate acids are water-soluble and insoluble in organic solvents.

When a base is added, the carboxylic acid is neutralized to its salt form, while the other compounds remain neutral. The salt then moves into the aqueous phase, and the neutral compounds stay in the organic phase. Acid-base extraction can also separate two weak acids or two weak bases when their pKa values are far enough apart. For weak acids, the stronger acid with the smaller pKa is converted to a salt using a weak base, while the weaker acid is not reacted much. The same idea applies to weak bases, but a weak acid is used to neutralize the stronger base.

Separating Mixtures with Solvent Extraction

separating-mixtures-with-solvent-extraction

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...

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

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...

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

Des vidéos complètes, axées sur le programme de cours pour les travaux pratiques de Chimie, adaptées à la fois aux professeurs et aux étudiants.

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

Learn how solvent extraction separates mixtures in organic chemistry, including liquid-liquid extraction, separatory funnels, partition coefficients, and acid-base extraction.

Separating Mixtures with Solvent Extraction | JoVE K12

Préparez l'enseignement de Extraction avec ce guide instructeur de 3 minutes. Couvre les principales étapes de préparation pour le laboratoire Chemistry sur JoVE Lab Manual.

Préparation de l'instructeur pour Extraction dans Chemistry - 8.0K+ vues | JoVE Lab Manual

Suivez les procédures étape par étape de Extraction dans cette vidéo de protocole étudiant de 19 minutes. Fait partie de la collection Chemistry sur JoVE Lab Manual.

Protocole étudiant de Extraction dans Chemistry - 67K+ vues | JoVE Lab Manual

Separating Mixtures with Solvent Extraction

Description

Transcript

Tags