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

Ekstraksiyon, bileşenleri bir karışımdan ayırmak için kullanılan bir tekniktir. Ekstraksiyona zaten aşinasınız. Çayı her demlediğinizde, çay yapraklarından sıcak suyunuza kafein ve aromalar gibi suda çözünür bileşikler çıkarıyorsunuz. Bu, katı-sıvı ekstraksiyonuna bir örnektir.
Sıvı-sıvı ekstraksiyonu, karışımın birbirine karışmayan iki sıvı fazda çözüldüğü başka bir ekstraksiyon türüdür. Çözücüler karışmaz olmalıdır, yani karışmazlar ve ayrı fazlardır. Sıvı-sıvı ekstraksiyonları, daha yoğun çözücünün dibe çökelmesi ve daha az yoğun çözücünün üstüne oturması için bir ayırıcı huni içinde gerçekleştirilir. Daha sonra, her bir çözünen bileşik, en çözünür olduğu faza geçecektir. Bu nedenle, farklı polaritelere sahip çözücülerin seçilmesi önemlidir.
Genel olarak, polar olmayan çözünen maddeler organik faza bölünür ve polar çözünen maddeler sulu faza bölünür. Bölme katsayısı, K, organik fazdaki çözünen konsantrasyonunun sulu fazdakine oranıdır. Çözünen maddeler ayrıldıktan sonra, iki farklı faz toplanır. Her iki aşamada da her bir bileşenin kalıntısı olma ihtimalinin yüksek olduğunu unutmayın.
Asit-baz ekstraksiyonu, asidik ve bazik bileşikleri çözünürlük farklılıklarına göre ayıran özel bir sıvı-sıvı ekstraksiyon türüdür. Bir asidin suda çözündüğünde bir proton bağışlayan bir bileşik olduğunu ve bir bazın bir protonu kabul eden bir bileşik olduğunu hatırlayın.
Asidik bileşikleri ayırmak için karışıma bir baz eklenir. Baz, asidik bileşikten bir proton kabul edecek ve onu iyonik hale getirecektir. Tersine, bir asit eklemek, bir protonu bazik bir bileşiğe aktaracaktır. Her iki durumda da, iyonik bileşik sulu faza geçecek ve nötr bileşikler organik faza ayrılacaktır. İyonik bileşik toplanır ve daha sonra orijinal bileşiğine geri dönüştürmek için protondan arındırılır veya yeniden protonlanır.
Bu laboratuvarda selüloz, benzoik asit ve kafein karışımını ayıracaksınız. İlk olarak, selülozu izole etmek için ekstraksiyon ve filtrasyon kullanacaksınız. Ardından, benzoik asit ve kafeini ayırmak için bir asit-baz ekstraksiyonu yapacaksınız.

Çıkarma

Çıkarma
Ekstraksiyon, organik kimyada bir hedef bileşiği izole etmek için kullanılan yaygın bir tekniktir. Ekstraksiyon işleminde, bir çözünen madde, reaksiyona girmemiş başlangıç malzemelerinden veya safsızlıklardan ayırmak için bir fazdan diğerine aktarılır. Ekstraksiyon ayrıca, yüksek kaynama noktasına sahip bir çözücü gibi buharlaşma yoluyla çıkarılması zor olan bir reaksiyon çözücüsünden bir çözünen maddenin izolasyonunu kolaylaştırmak için de kullanılır.<span style="color: rgb(0, 0, 0); yazı tipi ailesi: Roboto, RobotoDraft, Helvetica, Arial, sans-serif; yazı tipi boyutu: 13px; yazı tipi stili: normal; yazı tipi varyant bitişik harfleri: normal; font-variant-caps: normal; yazı tipi ağırlığı: 400; harf aralığı: normal; yetimler: 2; metin hizalama: başlat; metin girintisi: 0 piksel; metin dönüşümü: yok; beyaz boşluk: ön sarma; dullar: 2; kelime aralığı: 0 piksel; -webkit-metin-kontur genişliği: 0px; Arka plan rengi: RGB (255, 255, 255); metin-dekorasyon-stili: ilk; text-decoration-color: ilk; ekran: satır içi !önemli; şamandıra: yok;" > Genel olarak, üç tür ekstraksiyon vardır. İlk olarak, katı-sıvı ekstraksiyonunda, çözünen madde katı bir fazdan sıvı bir faza aktarılır. Sıvı-sıvı ekstraksiyonunda, bir çözünen madde bir sıvıdan diğerine aktarılır. Asit-baz ekstraksiyonunda, bir çözünen madde iyonik bir bileşiğe dönüştürülür ve organik bir fazdan sulu bir faza aktarılır. Ekstraksiyonun yaygın bir örneği, demlenen kahve veya çaydır. Kafeini, bitki tatlarını ve kokularını içeren katı faz, sıcak su ile sıvı faza ekstrakte edilir.
Sıvı-Sıvı Ekstraksiyonu
Bir sıvı-sıvı ekstraksiyonu, ya sulu bir fazda çözünen bir organik bileşiği bir organik çözücüye aktarır ya da reaksiyona girmemiş reaktanlar, tuzlar ve diğer suda çözünür safsızlıkları sulu faza aktarırken, ilgilenilen organik bileşiği organik fazda bırakır. Karışmayan sıvılar, iyice karıştırıldığında bile asla homojen bir çözelti oluşturmayan sıvılardır. Bunun yerine, karışmayan sıvılar, yağ ve su gibi farklı fazlara ayrılır.
Bir sıvı-sıvı ekstraksiyonu, sulu bir fazda çözünen organik bir bileşiği organik bir çözücüye aktarır. Sıvı-sıvı ekstraksiyonu gerçekleştirmek için, önce çözünen maddeyi içeren sulu çözelti bir ayırıcı huniye eklenir. Daha sonra, ayırıcı huniye suda çözünmeyen bir organik çözücü eklenir. Huninin içeriği iyice karıştırıldığında, organik bileşik, organik fazda sulu fazdan daha yüksek çözünürlüğüne bağlı olarak organik faza ayrılır.
İki çözücü birbirine karışmadığından, iki sıvı, yoğun sıvı altta ve daha az yoğun sıvı üstte olmak üzere ayrı katmanlar oluşturur. İki faz tekrar iki katmana yerleştikten sonra, ayırıcı huninin altındaki musluk açılarak ve bir katmanın dışarı akmasına izin verilerek ayrılırlar. Çözünen maddenin çıkarıldığı sıvıya rafinat denirken, çözünen maddeyi kazanan sıvıya ekstrakt denir.
Organik bileşik, her fazdaki çözünürlüğüne bağlı olarak iki katman arasında bölünür. Çözünen maddenin kimyasal potansiyeli iki fazda aynı olduğunda dengeye ulaşılır. Bir çözünen madde için bölme katsayısı, K, numunenin organik katmandaki konsantrasyonunun sulu fazdaki konsantrasyona bölünmesiyle elde edilen orandır. Bölme katsayısı, ekstraksiyonda kullanılan hem çözünen hem de çözücü çiftine bağlı bir sabittir. Bölme katsayısı, iki çözücünün her biri için çözünen maddenin tercihinin bir ifadesidir. Büyük bir bölme katsayısına sahip çözünen maddelerin, organik çözücü tabakasına ekstrakte edilme eğilimi daha yüksektir. Küçük bölme katsayılarına sahip çözünen maddeler sulu faza geçmeyi tercih eder.
Sıvı-sıvı ekstraksiyonu için hangi çözücü çiftinin kullanılacağının belirlenmesi hayati bir adımdır. Hangi çözücülerin kullanılacağını seçerken aşağıdakileri göz önünde bulundurun: İlk olarak, çözünen madde çözücü içinde sudan daha fazla çözünür olmalıdır. Bu nedenle, potansiyel bir çözücü çiftindeki çözünen maddenin bölme katsayısını bilmek gereklidir. İkincisi, çözücü çifti su ile karışmamalı ve karıştırıldığında homojen bir çözelti oluşturmamalıdır. Üçüncüsü, çözücüler inert olmalı ve çözünen madde ile reaksiyona girmemelidir. Çözücü ayrıca uçucu olmalıdır, böylece çözünen maddeden kolayca çıkarılabilir. Suyla karışmayan organik çözücü genellikle polar olmayan veya düşük polariteye sahiptir.
Üst ve alt katmanların kimliklerini belirlemek için çözücülerin yoğunluklarını bilmek de çok önemlidir. Klorlu organik çözücüler hariç, çoğu organik sıvının yoğunluğu sudan daha düşüktür ve ayırıcı huninin dibine çöker.
Asit-Baz Ekstraksiyonu
Asit-baz ekstraksiyonu, organik bileşikleri asit-baz özelliklerine göre ayıran bir sıvı-sıvı ekstraksiyon türüdür. Bir çözünen madde bir asit veya baz ise, pH değiştikçe yükü de değişir. Genel olarak, çoğu organik bileşik nötrdür ve bu nedenle organik çözücülerde suda olduğundan daha fazla çözünür. Bununla birlikte, organik bileşik iyonik hale gelirse, suda daha fazla çözünür hale gelir. Bu, bir organik asit veya baz bileşiğinin bir organik fazdan sulu bir faza ekstrakte edilmesinde faydalıdır.
Asit-baz ekstraksiyonu, çözünen maddeyi suda çözünür tuz formuna dönüştürerek ve böylece çözünürlüğünü değiştirerek bu özellikten yararlanır. Tekniğin etkili olabilmesi için organik bileşiğin ve tuzunun çözünürlüğü önemli ölçüde farklı olmalıdır.
Örneğin, bir organik karboksilik asit, bir amin ve nötr bir bileşik içeren bir karışım düşünün. Altı veya daha fazla karbondan oluşan karboksilik asitler suda çözünmez ve organik çözücülerde tamamen çözünür. Bununla birlikte, eşlenik bazları (iyonik bir bileşik) suda çözünür ve organik çözücülerde çözünmez. En az yedi karbondan oluşan bir amin suda çözünmez, ancak organik çözücülerde çözünür. Bu aminin eşlenik asidi (iyonik bir bileşik) suda çözünür ve organik çözücülerde çözünmez.
Bir baz ile reaksiyona girdiğinde, karboksilik asit tuz formuna nötralize edilir. Karışımdaki diğer bileşikler nötr kalır. Karboksilik asit bir tuza dönüştürüldüğünde, nötr bileşikler organik fazda kalırken sulu faza ayrılacaktır.
Asit-baz ekstraksiyonu, pKa'larında önemli bir fark olan iki zayıf asidi veya iki zayıf bazı ayırmak için de kullanılır. Asitler söz konusu olduğunda, küçük bir pKa değerine sahip olan nispeten daha güçlü asit, zayıf bir baz kullanılarak bir tuza nötralize edilir. Zayıf baz, zayıf asitle verimli bir şekilde reaksiyona girmez ve sadece daha güçlü asit bir tuza dönüştürülür. Daha sonra, ekstraksiyon sırasında tuz sulu faza ekstrakte edilir. İşlem, nispeten daha güçlü bazın zayıf bir asit kullanılarak bir tuza nötralize edildiği zayıf bazlar için benzer şekilde takip eder.
Başvuru
<ol>
	<li style="font-size:17px">Harris, D.C. (2015). Kantitatif Kimyasal Analiz. New York, NY: W.H. Freeman ve Şirketi.</li>
</ol>

Çıkarma
Ekstraksiyon, organik kimyada bir hedef bileşiği izole etmek için kullanılan yaygın bir tekniktir. Ekstraksiyon işleminde, bir çözünen madde aktarılır ...

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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

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column chromatography

Separating Mixtures by Polarity

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

hydrolysis of an ester

Soap Formation from Triglycerides

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

synthesis of luminol

Luminol Chemiluminescence in Forensics

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

esterification

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

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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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