Name: alcohol tests for primary, secondary, and tertiary
Uploaded: 2020-03-26T07:22:29.000Z
Duration: 3 min 32 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Physical Science

SC.912.P.8

SC.912.P.8.13

Identifying Alcohols

Alkohole to klasa cząsteczek organicznych posiadających co najmniej jedną hydroksylową grupę funkcyjną połączoną z atomem węgla. Metanol i etanol to dwa znane alkohole. Oba są alkoholami alifatycznymi, co oznacza, że pochodzą z węglowodoru i nie zawierają grupy benzenowej.
Istnieją trzy klasyfikacje alkoholi alifatycznych. Pierwszym z nich jest alkohol pierwszorzędowy, w którym grupa hydroksylowa jest połączona z atomem węgla, który jest połączony z jedną grupą opartą na węglu lub alkilem. W alkoholu drugorzędowym grupa hydroksylowa jest połączona z atomem węgla, który ma dwie grupy alkilowe. Wreszcie w trzeciorzędowym alkoholu grupa hydroksylowa jest połączona z atomem węgla z trzema grupami alkilowymi.
Alkohole mogą być również aromatyczne, w których grupa hydroksylowa jest połączona bezpośrednio z węglem pierścienia benzenowego. Najprostszą formą alkoholu aromatycznego jest fenol. Związki zawierające fenol są znane jako pochodne fenolu lub fenole.
Niektóre reakcje, którym poddawane są alkohole, można wykorzystać do ich rozróżnienia na podstawie widocznych różnic w wyniku reakcji. Jedną z takich reakcji jest test chlorku żelaza, który bada obecność fenoli. Po dodaniu chlorku żelaza do fenolu tworzy się fioletowy kompleks żelaza-trójfenolu. Nie obserwuje się tego, gdy dodaje się go do alkoholu alifatycznego.
Inną przydatną reakcją jest test Jonesa, który służy do identyfikacji pierwszorzędowych i drugorzędowych alkoholi alifatycznych. Odczynnik Jonesa, mieszanina kwasu siarkowego i trójtlenku chromu w wodzie, jest silnym utleniaczem. Reaguje z alkoholami pierwszorzędowymi, tworząc aldehydy - które następnie tworzą kwasy karboksylowe - i reaguje z alkoholami drugorzędowymi, tworząc ketony. Dodanie odczynnika Jones do pierwszorzędowych i drugorzędowych alkoholi powoduje, że roztwór zmienia barwy z pomarańczowego na ciemnozielony. Alkohole trzeciorzędowe nie reagują z odczynnikiem Jonesa, ponieważ są odporne na utlenianie.
Wreszcie możemy wyróżnić alkohole alifatyczne za pomocą testu Lucasa. Odczynnik Lucasa, który jest mieszaniną chlorku i kwasu solnego, reaguje z alkoholami drugorzędowymi i trzeciorzędowymi w reakcji substytucji nukleofilowej SN1. Chlorek koordynuje się z tlenem hydroksylowym, tworząc doskonałą grupę opuszczającą. Po wyeliminowaniu pozostaje dodatnio naładowany karbokation. Następnie jon chloru atakuje karbokation, tworząc chlorek alkilu, który jest nierozpuszczalny w wodzie i wydaje się mętny.
Alkohole trzeciorzędowe reagują natychmiast z odczynnikiem Lucasa, tworząc oleistą warstwę w temperaturze pokojowej. Alkohole drugorzędowe dają pozytywny wynik po kilku sekundach do kilku minut. Alkohole pierwszorzędowe dają wynik negatywny, chyba że zostaną podgrzane.
W tym laboratorium użyjesz testu chlorku żelaza, testu Jonesa i testu Lucasa, aby zidentyfikować nieznany alkohol.

identyfikacja alkoholi

<h4>alkohole</h4>
Alkohole to związki organiczne, które są jednymi z najbardziej rozpoznawalnych i znanych, ponieważ mają szerokie zastosowania i zastosowania w życiu codziennym. Alkohole to cząsteczki organiczne zawierające hydroksylową grupę funkcyjną połączoną z grupą alkilową lub arylową (ROH). Jeśli węgiel hydroksylowy ma tylko jedną grupę R, jest znany jako alkohol pierwszorzędowy. Jeśli ma dwie grupy R, jest alkoholem drugorzędowym, a jeśli ma trzy grupy R, jest to alkohol trzeciorzędowy. Podobnie jak wiele innych związków organicznych, alkohole mogą być również aromatyczne, ponieważ zawierają pierścień benzenowy. Najprostszym alkoholem aromatycznym jest fenol.
Identyfikacja alkoholu w chemii organicznej może być osiągnięta poprzez wykorzystanie różnych właściwości rodzajów alkoholi. Chociaż można stosować różne metody analizy oprzyrządowania, takie jak magnetyczny rezonans jądrowy (NMR), można również zastosować inne testy jakościowe. Łącząc ze sobą te testy, tożsamość alkoholu można określić w podobny sposób, w jaki można zidentyfikować aldehydy i ketony.
<h4>Test chlorku żelaza</h4>
Jedną z metod rozróżniania alkoholu alifatycznego i aromatycznego jest użycie chlorku żelaza(III). Związek chlorku żelaza nadaje roztworowi czerwono-pomarańczowy wygląd. W obecności alkoholu aromatycznego, takiego jak fenol, atomy chlorku są zastępowane alkoholem aromatycznym, zmieniając właściwości koordynacyjne środkowego atomu żelaza. Spowoduje to zmianę koloru roztworu na fioletowy. Alkohole alifatyczne nie reagują z chlorkiem żelaza(III), a zatem roztwór pozostaje czerwono-pomarańczowy.
<h4>Test Jonesa</h4>
Test Jonesa wykorzystuje trójtlenek chromu w obecności kwasu siarkowego, aby działał jako silny środek utleniający. W obecności odczynnika Jonesa alkohol pierwszorzędowy jest najpierw przekształcany w aldehyd, a następnie w kwas karboksylowy, podczas gdy alkohol drugorzędowy zostanie utleniony w keton. Stopień utlenienia chromu jest kluczem do tego testu. Chrom znajduje się na stopniu utlenienia +6 w odczynniku Jonesa. Kompleksy Cr(VI) w odczynniku nadają mu jaskrawy czerwonawy, pomarańczowy kolor.
W procesie reakcji chrom ulega redukcji z Cr(VI) do stopnia utlenienia +3 — Cr(III). Po pierwsze, alkohol i kwas chromowy tworzą ester chromianowy. Następnie zasada (H2O) rozszczepia wiązanie C-H alkoholu, tworząc grupę karbonylową, jednocześnie redukując Cr(VI) do Cr(IV). Węgiel alkoholu ulega utlenianiu 2-elektronowemu, a Cr(IV) ulega redukcji 2-elektronowej, więc jest to etap redukcji-utleniania.
Cr(IV) uczestniczy w dalszych etapach utleniania i ostatecznie ulega redukcji do Cr(III). Cr(III) jest często obecny w postaci jonów heksakwachromu(III) - [Cr(H2O)6]3+ - i kompleksów Cr(III), w których cząsteczki H2O są zastępowane przez jeden lub więcej jonów siarczanowych - [Cr(H2O)5 (SO4)]+. Kompleksy te nadają Cr(III) charakterystyczny zielony kolor.
Alkohole trzeciorzędowe nie reagują z chromem, a zatem nie wytrąca się osad, dzięki czemu roztwór pozostaje pomarańczowy. Dlatego test Jonesa może pomóc w odróżnieniu alkoholi pierwszorzędowych i drugorzędowych od alkoholi trzeciorzędowych.
<h4>Test Lucasa</h4>
Test Lucasa wykorzystuje chlorek(II) w obecności kwasu solnego jako odczynnik. W obecności alkoholu, odczynnik Lucas będzie halogenował alkohol, tworząc nierozpuszczalny produkt w roztworach wodnych. Szybkość reakcji w tym przypadku jest w dużym stopniu zależna od powstania karbokationu spowodowanego utratą hydroksylu w postaci wody. Karbokation utworzony przez pierwszorzędowy alkohol jest niestabilny, a zatem nie nastąpi łatwo. Powoduje to brak obserwowalnej reakcji w temperaturze pokojowej. Alkohol trzeciorzędowy utworzy stabilny karbokation, powodując szybką reakcję po dodaniu odczynnika Lucasa. Powoduje to pojawienie się drugiej fazy w mieszaninie reakcyjnej, ponieważ końcowy produkt halogenowy jest nierozpuszczalny w wodzie. Alkohole drugorzędowe utworzą mniej stabilny karbokation niż alkohole trzeciorzędowe, ale reakcja zajdzie w temperaturze pokojowej w ciągu kilku minut. Dlatego test Lucasa może pomóc w rozróżnieniu między alkoholami pierwszorzędowymi, drugorzędowymi i trzeciorzędowymi.
<h4>Odwołania</h4>
<ol>
	<li style="font-size:17px">Streitwieser, A., Heathcock, C.H., Kosower, E.M. (1998). Wprowadzenie do chemii organicznej. Upper Saddle River, NJ: Prentice Hall.</li>
</ol>

Identyfikacja alkoholi

Alkohole
Alkohole to związki organiczne, które są jednymi z najbardziej rozpoznawalnych i znanych, ponieważ mają szerokie zastosowania i zastosowania w codziennym ...

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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 behavior instead of relying only on instrument-based methods such as NMR. By combining several qualitative tests, the identity of an alcohol can be determined in a way similar to how aldehydes and ketones are identified.

The ferric chloride test helps tell aromatic alcohols from aliphatic alcohols. Iron(III) chloride starts as a red-orange solution. If an aromatic alcohol such as phenol is present, the chloride atoms are replaced and the solution turns purple. Aliphatic alcohols do not react in this test, so the color stays red-orange.

The Jones test uses chromium trioxide with sulfuric acid as a strong oxidizing reagent. A primary alcohol is oxidized first to an aldehyde and then to a carboxylic acid. A secondary alcohol is oxidized to a ketone. Chromium starts in the +6 oxidation state, which gives the reagent its reddish-orange color, and is reduced to Cr(III), which is green. Tertiary alcohols do not react, so the solution remains orange. This makes the Jones test useful for separating primary and secondary alcohols from tertiary alcohols.

The Lucas test uses zinc(II) chloride in hydrochloric acid. It halogenates the alcohol and produces an insoluble product in water. The test depends on carbocation formation when the hydroxyl group leaves as water. Primary alcohols do not show a visible reaction at room temperature because their carbocations are unstable. Tertiary alcohols react quickly because their carbocations are more stable, and a second layer appears. Secondary alcohols react more slowly and usually take a few minutes. This test helps distinguish primary, secondary, and tertiary alcohols.

Alcohol Tests for Primary, Secondary, and Tertiary

alcohol-tests-for-primary-secondary-and-tertiary

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chemistry

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Learn how ferric chloride, Jones, and Lucas tests distinguish aromatic, primary, secondary, and tertiary alcohols using color change and reaction rate.

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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 ...

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.

Alcohol Tests for Primary, Secondary, and Tertiary

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