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

אלכוהולים הם סוג של מולקולות אורגניות בעלות לפחות קבוצה פונקציונלית הידרוקסילית אחת המחוברת לאטום פחמן. מתנול ואתנול הם שני אלכוהולים מוכרים. שניהם אלכוהולים אליפטיים, כלומר הם נגזרים מפחמימנים ואינם מכילים קבוצת בנזן.
ישנם שלושה סיווגים של אלכוהולים אליפטיים. הראשון הוא אלכוהול ראשוני, שבו קבוצת ההידרוקסיל מחוברת לאטום פחמן המחובר לקבוצה אחת מבוססת פחמן, או אלקיל. באלכוהול משני, קבוצת ההידרוקסיל מחוברת לאטום פחמן שיש לו שתי קבוצות אלקיל. לבסוף, באלכוהול שלישוני, קבוצת ההידרוקסיל מחוברת לאטום פחמן עם שלוש קבוצות אלקיל.
אלכוהולים יכולים להיות גם ארומטיים, בהם קבוצת הידרוקסיל מחוברת ישירות לפחמן של טבעת בנזן. הצורה הפשוטה ביותר של אלכוהול ארומטי היא פנול. תרכובות המכילות פנול ידועות כנגזרות פנול או פנולים.
ניתן להשתמש בתגובות מסוימות שעוברות אלכוהול כדי להבחין ביניהן על סמך הבדלים נראים לעין בתוצאת התגובה. תגובה אחת כזו היא בדיקת כלוריד ברזל, הבודקת נוכחות של פנולים. כאשר מוסיפים ברזל כלוריד לפנול, נוצר קומפלקס ברזל-שלושה פנולים סגול. זה לא נצפה כאשר מוסיפים אותו לאלכוהול אליפטי.
תגובה שימושית נוספת היא מבחן ג'ונס, המשמש לזיהוי אלכוהולים אליפטיים ראשוניים ומשניים. המגיב של ג'ונס, תערובת של חומצה גופרתית וכרום תלת-חמצני במים, הוא חומר מחמצן חזק. הוא מגיב עם אלכוהולים ראשוניים ליצירת אלדהידים - שיוצרים לאחר מכן חומצות קרבוקסיליות - והוא מגיב עם אלכוהולים משניים ליצירת קטונים. התוספת של מגיב ג'ונס לאלכוהול ראשוני ומשניים גורמת לתמיסה לשנות את צבעיה מכתום לירוק כהה. אלכוהולים שלישוניים אינם מגיבים עם המגיב של ג'ונס מכיוון שהם עמידים בפני חמצון.
לבסוף, אנו יכולים להבחין בין אלכוהולים אליפטיים באמצעות מבחן לוקאס. המגיב של לוקאס, שהוא תערובת של אבץ כלורי וחומצה הידרוכלורית, מגיב עם אלכוהולים משניים ושלישוניים באמצעות תגובת החלפה נוקלאופילית SN1. האבץ כלוריד מתואם לחמצן ההידרוקסיל כדי ליצור קבוצת יציאה מצוינת. לאחר חיסולו, נותר פחמימה טעונה חיובית. לאחר מכן, יון כלור תוקף את הקרבוקציה ליצירת אלקיל כלוריד, שאינו מסיס במים ונראה עכור.
אלכוהול שלישוני מגיב מיד עם המגיב של לוקאס ליצירת שכבה שמנונית בטמפרטורת החדר. אלכוהולים משניים נותנים תוצאה חיובית לאחר מספר שניות עד מספר דקות. אלכוהולים ראשוניים נותנים תוצאה שלילית אלא אם כן הם מחוממים.
במעבדה זו, תשתמש בבדיקת כלוריד ברזל, מבחן ג'ונס ומבחן לוקאס כדי לזהות אלכוהול לא ידוע.

זיהוי אלכוהולים

<h4>אלכוהולים</h4>
אלכוהולים הם תרכובות אורגניות שהן בין המוכרות והמוכרות ביותר, שכן יש להן יישומים ושימושים נרחבים בחיי היומיום. אלכוהולים הם מולקולות אורגניות המכילות קבוצה פונקציונלית הידרוקסיל המחוברת לקבוצת אלקיל או אריל (ROH). אם לפחמן הידרוקסיל יש רק קבוצת R אחת, זה ידוע כאלכוהול ראשוני. אם יש לו שתי קבוצות R, הוא אלכוהול משני, ואם יש לו שלוש קבוצות R, הוא אלכוהול שלישוני. כמו תרכובות אורגניות רבות אחרות, גם אלכוהולים יכולים להיות ארומטיים בכך שהם מכילים טבעת בנזן. האלכוהול הארומטי הפשוט ביותר הוא פנול.
זיהוי אלכוהול בכימיה אורגנית יכול להיות מושג על ידי ניצול התכונות השונות של סוגי אלכוהולים. בעוד שניתן להשתמש בשיטות ניתוח מכשור שונות, כגון תהודה מגנטית גרעינית (NMR), ניתן להשתמש גם בבדיקות איכותניות אחרות. על ידי צימוד בדיקות אלה יחד, ניתן לקבוע את זהותו של אלכוהול באופן דומה לאופן שבו אלדהידים וקטונים יכולים להיות מזוהים.
<h4>מבחן כלוריד ברזל</h4>
שיטה אחת להבדיל בין אלכוהול אליפטי לאלכוהול ארומטי היא באמצעות ברזל(III) כלוריד. תרכובת הברזל כלוריד מעניקה לתמיסה מראה אדום-כתום. בנוכחות אלכוהול ארומטי, כמו פנול, אטומי הכלוריד מוחלפים על ידי אלכוהול ארומטי, שינוי תכונת התיאום של אטום הברזל המרכזי. פעולה זו משנה את צבע התמיסה לצבע סגול. אלכוהולים אליפטיים לא יגיבו עם ברזל(III) כלוריד, ולכן התמיסה נשארת אדומה-כתומה.
<h4>מבחן ג'ונס</h4>
מבחן ג'ונס משתמש בתלת-תחמוצת הכרום בנוכחות חומצה גופרתית כדי לפעול כחומר מחמצן רב עוצמה. בנוכחות מגיב ג'ונס, אלכוהול ראשוני מומר תחילה לאלדהיד ולאחר מכן לחומצה קרבוקסילית, בעוד שאלכוהול משני יתחמצן לקטון. מצב החמצון של כרום הוא המפתח לבדיקה זו. כרום נמצא במצב חמצון +6 בריאגנט של ג'ונס. מתחמי Cr(VI) בריאגנט מעניקים לו את צבעו האדמדם הכתום הבוהק.
בתהליך התגובה, כרום מופחת מ-Cr(VI) למצב חמצון +3 – Cr(III). ראשית, האלכוהול והחומצה הכרומית יוצרים אסטר כרומט. לאחר מכן, בסיס (H2O) מנתק את הקשר C-H של האלכוהול, ויוצר את קבוצת הקרבוניל תוך הפחתת Cr(VI) ל- Cr(IV). הפחמן של האלכוהול עובר חמצון של 2 אלקטרונים, וה-Cr(IV) עובר חיזור של 2 אלקטרונים, כך שזהו שלב חיזור-חמצון.
Cr(IV) משתתף בשלבי חמצון נוספים ובסופו של דבר מצטמצם ל-Cr(III). Cr(III) קיים לעתים קרובות כיוני hexaaquachromium(III) — [Cr(H2O)6]3+ — וקומפלקסים Cr(III), שבהם מולקולות H2O מוחלפות על ידי יון סולפט אחד או יותר — [Cr(H2O)5(SO4)]+. קומפלקסים אלה נותנים Cr(III) את הצבע הירוק האופייני.
אלכוהולים שלישוניים אינם מגיבים עם כרום, ולכן לא נוצר משקע, מה ששומר על התמיסה כתומה. לכן, מבחן ג'ונס יכול לעזור להבדיל בין אלכוהולים ראשוניים ומשניים לבין אלכוהולים שלישוניים.
<h4>מבחן לוקאס</h4>
בדיקת לוקאס משתמשת באבץ(II) כלוריד בנוכחות חומצה הידרוכלורית כמגיב. בנוכחות אלכוהול, מגיב לוקאס יהיה הלוגנים את האלכוהול, מה שהופך מוצר מסיס בתמיסות מימיות. קצב התגובה לכך תלוי מאוד בהיווצרות קרבוקטיון הנגרם על ידי אובדן ההידרוקסיל כמים. קרבוקטיון שנוצר על ידי אלכוהול ראשוני אינו יציב, ולכן לא יתרחש בקלות. התוצאה היא שאין תגובה נצפית בטמפרטורת החדר. אלכוהול שלישוני ייצור קרבוקטיון יציב, וכתוצאה מכך תגובה מהירה עם הוספת מגיב לוקאס. התוצאה היא שלב שני המופיע בתערובת התגובה מכיוון שהתוצר ההלוגני הסופי אינו מסיס במים. אלכוהולים משניים ייצרו קרבוקטיון פחות יציב מאשר אלכוהולים שלישוניים, אך התגובה תתרחש בטמפרטורת החדר תוך דקות ספורות. לכן, מבחן לוקאס יכול לעזור להבדיל בין אלכוהול ראשוני, משני ושלישוני.
<h4>הפניות</h4>
<ol>
	<li style="font-size:17px">Streitwieser, A., Heathcock, C.H., Kosower, E.M. (1998). מבוא לכימיה אורגנית. נהר האוכף העליון, ניו ג'רזי: פרנטיס הול.</li>
</ol>

Alcohols
Alcohols are organic compounds that are amongst the most recognizable and familiar, as they have wide-ranging applications and uses in everyday ...

Education

JoVE Lab Manual

Chemistry

כימיה

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

Alcohol Tests for Primary, Secondary, and Tertiary | JoVE K12

התכוננו ללמד את זיהוי אלכוהולים עם מדריך מדריכים זה באורך 7 דקות. כולל שלבי הכנה מרכזיים עבור מעבדת Chemistry ב-JoVE Lab Manual.

הכנת מדריך עבור זיהוי אלכוהולים ב-Chemistry - 13K+ צפיות | JoVE Lab Manual

עקבו אחר הנהלים של זיהוי אלכוהולים שלב אחר שלב בסרטון פרוטוקול סטודנטים זה באורך 12 דקות. חלק מאוסף Chemistry ב-JoVE Lab Manual.

פרוטוקול סטודנטים עבור זיהוי אלכוהולים ב-Chemistry - 87K+ צפיות | 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.

Alcohol Tests for Primary, Secondary, and Tertiary

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