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

الاستخراج هو تقنية لفصل المكونات عن الخليط. أنت بالفعل على دراية بالاستخراج. في أي وقت تنقع فيه الشاي ، فإنك تستخرج مركبات قابلة للذوبان في الماء ، مثل الكافيين والنكهات ، من أوراق الشاي إلى الماء الساخن. هذا مثال على استخراج السائل الصلب. 
استخراج السائل السائل هو نوع آخر من الاستخراج حيث يتم إذابة الخليط في مرحلتين سائلتين غير قابلتين للامتزاج. يجب أن تكون المذيبات غير قابلة للامتزاج ، مما يعني أنها لا تختلط وهي مراحل منفصلة. يتم إجراء عمليات الاستخراج السائل السائل في قمع منفصل بحيث يستقر المذيب الأكثر كثافة في القاع وسيجلس المذيب الأقل كثافة في الأعلى. بعد ذلك ، سينتقل كل مركب مذاب إلى المرحلة التي يكون فيها أكثر قابلية للذوبان. لذلك ، من المهم اختيار المذيبات ذات الأقطاب المختلفة. 
بشكل عام ، ستنقسم المواد المذابة غير القطبية إلى المرحلة العضوية ، وسوف تنقسم المواد المذابة القطبية إلى المرحلة المائية. معامل التقسيم ، K ، هو نسبة تركيز المذاب في الطور العضوي إلى تلك الموجودة في المرحلة المائية. بمجرد فصل المواد المذابة ، يتم جمع المرحلتين المختلفتين. ضع في اعتبارك أنه من المحتمل أن يكون هناك بقايا لكل مكون في كلتا المرحلتين. 
الاستخراج الحمضي القاعدي هو نوع خاص من الاستخراج السائل السائل الذي يفصل بين المركبات الحمضية والأساسية بناء على اختلافات الذوبان. تذكر أن الحمض هو مركب يتبرع ببروتون عند إذابته في الماء ، والقاعدة عبارة عن مركب يقبل البروتون. 
لفصل المركبات الحمضية ، تضاف قاعدة إلى الخليط. ستقبل القاعدة بروتونا من المركب الحمضي ، مما يجعله أيونيا. على العكس من ذلك ، فإن إضافة حمض من شأنه أن ينقل البروتون إلى مركب أساسي. في كلتا الحالتين ، سينتقل المركب الأيوني إلى الطور المائي ، وتنقسم المركبات المحايدة إلى المرحلة العضوية. يتم جمع المركب الأيوني ثم إما إزالة البروتون أو إعادة البروتون لتحويله مرة أخرى إلى مركبه الأصلي. 
في هذا المختبر ، ستفصل مزيجا من السليلوز وحمض البنزويك والكافيين. أولا ، ستستخدم الاستخراج والترشيح لعزل السليلوز. بعد ذلك ، ستقوم بإجراء استخراج القاعدة الحمضية لفصل حمض البنزويك والكافيين.

إستخلاص

الاستخراج
الاستخراج هو تقنية شائعة تستخدم في الكيمياء العضوية لعزل المركب المستهدف. في عملية الاستخراج ، يتم نقل المذاب من مرحلة إلى أخرى لفصله عن مواد البداية أو الشوائب غير المتفاعلة. يستخدم الاستخراج أيضا لتسهيل عزل المذاب عن مذيب التفاعل الذي يصعب إزالته عن طريق التبخر ، مثل المذيب ذو نقطة الغليان العالية. <span style="color: rgb(0, 0, 0); font-family: Roboto, RobotoDraft, Helvetica, Arial, sans-serif; font-size: 13px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: pre-wrap; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;"> بشكل عام ، هناك ثلاثة أنواع من عمليات الاستخراج. أولا ، في الاستخراج السائل الصلب ، يتم نقل المذاب من مرحلة صلبة إلى مرحلة سائلة. في الاستخراج السائل السائل ، يتم نقل المذاب من سائل إلى آخر. في الاستخراج الحمضي القاعدي ، يتم تحويل المذاب إلى مركب أيوني ونقله من مرحلة عضوية إلى مرحلة مائية. من الأمثلة الشائعة على الاستخراج تخمير القهوة أو الشاي. يتم استخراج المرحلة الصلبة ، التي تحتوي على الكافيين والنكهات النباتية والروائح ، عن طريق الماء الساخن في الطور السائل. 
استخراج السائل 
ينقل الاستخراج السائل السائل إما مركبا عضويا مذاب في طور مائي إلى مذيب عضوي ، أو يستخدم لنقل المواد المتفاعلة والأملاح والشوائب الأخرى القابلة للذوبان في الماء إلى المرحلة المائية مع ترك المركب العضوي ذي الأهمية في المرحلة العضوية. السوائل غير القابلة للامتزاج هي سوائل لا تشكل محلولا متجانسا أبدا ، حتى عند خلطها جيدا. بدلا من ذلك ، تنفصل السوائل غير القابلة للامتزاج إلى مراحل مختلفة ، مثل الزيت والماء. 
ينقل الاستخراج السائل السائل مركبا عضويا يذوب في مرحلة مائية إلى مذيب عضوي. لإجراء استخراج السائل السائل ، أولا ، يضاف المحلول المائي الذي يحتوي على المذاب إلى قمع منفصل. بعد ذلك ، يضاف مذيب عضوي غير قابل للذوبان في الماء إلى القمع الفاصل. عندما يتم خلط محتويات القمع جيدا ، ينقسم المركب العضوي إلى المرحلة العضوية بناء على قابليته العالية للذوبان في المرحلة العضوية من المرحلة المائية. 
نظرا لأن المذيبين غير قابلين للامتزاج ، فإن السائلين يشكلان طبقات منفصلة ، مع وجود السائل الكثيف في الأسفل والسائل الأقل كثافة في الأعلى. بمجرد أن تستقر المرحلتان مرة أخرى في طبقتين ، يتم فصلهما عن طريق فتح محبس في الجزء السفلي من القمع الفاصل والسماح لطبقة واحدة بالتدفق. يسمى السائل الذي تمت إزالة المذاب بالرافينات ، بينما يسمى السائل الذي اكتسب المذاب بالمستخلص. 
يتم تقسيم المركب العضوي بين الطبقتين بناء على قابليته للذوبان في كل مرحلة. يتم الوصول إلى التوازن عندما تكون الإمكانات الكيميائية للمذاب هي نفسها في المرحلتين. معامل التقسيم للمذاب ، K ، هو نسبة تركيز العينة في الطبقة العضوية مقسومة على التركيز في الطور المائي. معامل التقسيم هو ثابت يعتمد على كل من المذاب وزوج المذيبات المستخدمة في الاستخراج. معامل التقسيم هو تعبير عن تفضيل المذاب لكل من المذيبين. المواد المذابة ذات معامل التقسيم الكبير لها ميل أعلى ليتم استخراجها في طبقة المذيبات العضوية. تفضل المواد المذابة ذات معاملات التقسيم الصغيرة الانتقال إلى المرحلة المائية. 
يعد تحديد زوج المذيبات الذي يجب استخدامه لاستخراج السائل السائل خطوة حيوية. ضع في اعتبارك ما يلي عند اختيار المذيبات التي يجب استخدامها: أولا ، يجب أن يكون المذاب أكثر قابلية للذوبان في المذيب منه في الماء. لذلك ، من الضروري معرفة معامل تقسيم المذاب في زوج مذيب محتمل. ثانيا ، يجب أن يكون زوج المذيبات غير قابل للامتزاج في الماء ولا يشكل محلولا متجانسا عند الخلط. ثالثا ، يجب أن تكون المذيبات خاملة ولا تتفاعل مع المذاب. يجب أن يكون المذيب أيضا متطارا بحيث يمكن إزالته من المذاب بسهولة. يمتلك المذيب العضوي غير القابل للامتزاج بالماء عموما قطبية غير قطبية أو منخفضة. 
من الأهمية بمكان أيضا معرفة كثافات المذيبات لتحديد هويات الطبقات العليا والسفلية. معظم السوائل العضوية لها كثافة أقل من الماء ، باستثناء المذيبات العضوية المكلورة ، وسوف تستقر في قاع القمع الفاصل. 
استخراج القاعدة الحمضية
استخراج الحمض القاعدي هو نوع من الاستخراج السائل السائل الذي يفصل المركبات العضوية بناء على خصائصها الحمضية القاعدية. إذا كان المذاب حمضا أو قاعدة ، فإن شحنته تتغير مع تغير الرقم الهيدروجيني. بشكل عام ، تكون معظم المركبات العضوية محايدة ، وبالتالي فهي أكثر قابلية للذوبان في المذيبات العضوية مما هي عليه في الماء. ومع ذلك ، إذا أصبح المركب العضوي أيونيا ، فإنه يصبح أكثر قابلية للذوبان في الماء. هذا مفيد في استخراج حمض عضوي أو مركب أساسي من مرحلة عضوية إلى مرحلة مائية. 
يسخر استخراج القاعدة الحمضية هذه الخاصية عن طريق تحويل المذاب إلى شكل ملح قابل للذوبان في الماء ، وبالتالي تغيير قابليته للذوبان. يجب أن تكون قابلية ذوبان المركب العضوي وملحه مختلفة بشكل كبير حتى تكون التقنية فعالة. 
على سبيل المثال ، ضع في اعتبارك خليطا يحتوي على حمض كربوكسيلي عضوي وأمين ومركب محايد. الأحماض الكربوكسيلية التي تتكون من ستة كربون أو أكثر غير قابلة للذوبان في الماء وقابلة للذوبان تماما في المذيبات العضوية. ومع ذلك ، فإن قواعدها المترافقة (مركب أيوني) قابلة للذوبان في الماء وغير قابلة للذوبان في المذيبات العضوية. الأمين الذي يتكون من سبعة كربون على الأقل غير قابل للذوبان في الماء ولكنه قابل للذوبان في المذيبات العضوية. الحمض المترافق لهذا الأمين (مركب أيوني) قابل للذوبان في الماء وغير قابل للذوبان في المذيبات العضوية. 
عندما يتفاعل مع قاعدة ، يتم تحييد حمض الكربوكسيل إلى شكله الملحي. تظل المركبات الأخرى في الخليط محايدة. بمجرد أن يتحول حمض الكربوكسيل إلى ملح ، فإنه سينقسم إلى المرحلة المائية ، بينما تظل المركبات المحايدة في المرحلة العضوية. 
يستخدم استخراج الحمض القاعدي أيضا لفصل حمضين ضعيفين أو قاعدتين ضعيفتين مع اختلاف كبير في pK a . في حالة الأحماض ، يتم تحييد الحمض الأقوى نسبيا ، الذي له قيمة pKa صغيرة ، إلى ملح باستخدام قاعدة ضعيفة. لا تتفاعل القاعدة الضعيفة بكفاءة مع الحمض الأضعف ، ويتم تحويل الحمض الأقوى فقط إلى ملح. ثم يتم استخراج الملح في المرحلة المائية أثناء الاستخراج. يتبع العملية بالمثل لقواعد ضعيفة, حيث القاعدة قوية نسبيا يكون تحييد إلى ملح يستعمل حامض ضعيفة. 
المراجع
<ol>
	<li style="font-size:17px">هاريس ، العاصمة (2015). التحليل الكيميائي الكمي. نيويورك ، نيويورك: دبليو إتش فريمان وشركاه. </li>
</ol>

إستخلاص
الاستخراج هو تقنية شائعة تستخدم في الكيمياء العضوية لعزل المركب المستهدف. في عملية الاستخراج ، يتم نقل المذاب ...

Education

JoVE Lab Manual

Chemistry

الكيمياء

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 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

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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

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

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

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

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Separating Mixtures with Solvent Extraction

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