Experiment 9 Formal Report on Classification test of hydroxyl-containing and carbonyl-containing organic compounds

Classification Tests for HydroxylAnd Carbonyl-Containing Compounds Dupaya, Julian Victor M., Estacio, Jerwin Caesar A., Farnacio, Rebecca Ruth, Gabito, Jose Luis F., F., Gallo, Cian Carlo M., Galvez, Joshua M. Group no.4, 2D-Medical Technology, Faculty of Pharmacy, University of Santo Tomas

Abstract Hydroxyl- or carbonyl- containing samples were given to the group for analysis. Hydroxyl group refers to a functional group containing OH- when it is a substituent in an organic compound whereas carbonyl group refers to a divalent chemical unit consisting of a carbon and an oxygen atom connected by a double bond. bond. Hydroxyl group is the characteristic functional group of alcohols and phenols while carbonyl group is the characteristic functional group of aldehydes and ketones. The samples were analyzed through tests involving solubility of alcohols in water, Lucas Test, Chromic Acid Test (Jones Oxidation), 2,4-Dinitrophenylhydrazone (2,4-DNP) (2,4-DNP) Test, Fehling’s Test, Tollens’ Silver Mirror Test, and Iodoform Test. Lucas Test differentiates primary, secondary, and tertiary alcohols. Chromic Acid Test is a test for oxidizables or any compounds that possess reducing property 2,4-DNP Test is a test for aldehydes and ketones. Fehling’s Test and Tollens’ Silver Mirror Test ar e ar e tests for aldehydes. Iodoform test is a test for methyl carbinol and methyl carbonyl groups.

Introduction

Hydroxyl group is used to describe the functional the functional group – group –OH OH when it is a substituent in an organic compound. compound. Hydroxyl groups are especially important in biological chemistry because of their tendency to form hydrogen form hydrogen bonds both as donor and acceptor. This property is also related to their ability to increase hydrophilicity increase hydrophilicity and water solubility. solubility. The hydroxyl group is especially predominant in the family of molecules known as carbohydrates. Hydroxyl group is the characteristic functional group of alcohols and phenols.

Figure 1 Structure of a Hydroxylcontaining compound

Alcohols are characterized characterized by one or more hydroxyl (−OH) groups attached to a carbon atom of an alkyl group (hydrocarbon chain). Alcohols may be considered as organic derivatives of water (H2O) in which one of the hydrogen atoms has been replaced by an alkyl group, typically represented by R in organic structures. Because of hydrogen bonding, bonding, alcohols tend to have higher boiling points than comparable hydrocarbons and ethers Alcohols, like water, can show either acidic or basic properties at the O-H group. With a pKa of around 16-19 they

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are generally slightly weaker acids than water, but water, but they are still able to react with strong bases such as sodium as sodium hydride or reactive metals such as sodium. sodium. The salts that result are called alkoxides. Alcohols have an odor that is often described as “biting” and as “hanging” in the nasal passages. There are three classifications of alcohols by the carbon to which the hydroxyl group is attached. Primary alcohols are those in which the hydroxyl group is attached to the carbon with only one carbon attached. Secondary alcohols are compounds in which the OH- is attached to a carbon which has two other carbons attached. Tertiary alcohols are compounds in which a hydroxyl group is attached to a carbon with three attached carbons. Phenols are aromatic are aromatic compounds in which a hydroxide group is directly bonded to an aromatic ring system. They are very weak acids, acids, and like alcohols, alcohols, form ethers and esters. esters. The main phenols are phenol itself, cresol, resorcinol, resorcinol, pyrogallol, and picric acid. Phenol itself (C 6H5OH), also known as carbolic acid, is a white, hygroscopic crystalline solid, isolable from coal tar, but made by acid hydrolysis of cumene hydroperoxide, or by fusion of sodium benzenesulfonate with sodium hydroxide. Formerly used as an antiseptic, phenol antiseptic, phenol has more latterly been

The hydroxylcontaining compounds used in the experiment are ethanol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isopropyl alcohol, and benzyl alcohol. Ethanol, C 2H5OH, (also known as ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol) is the second member of the aliphatic alcohol series. It is a clear, colorless, volatile, and flammable liquid which is completely miscible with water and organic solvents. It burns with a smokeless blue flame that is not always visible in normal light. Ethanol has widespread use as a solvent of substances intended for human contact or consumption, including scents, flavorings, colorings, and medicines. In chemistry, it is both an essential solvent and a feedstock for the synthesis of other products. Figure 2 Structure of Ethanol

N-butyl alcohol (also known as nbutanol, 1-Butanol or 1-butyl alcohol) is a four carbon straight chain alcohol. It is a volatile, clear liquid with a strong alcoholic odor, and is miscible with







oxidizers. N-butanol is used as a direct solvent and as an intermediate in the manufacture of other organic chemicals. Figure 3 Structure of n-butyl alcohol

Sec-butyl alcohol with the formula CH3CH(O CH(OH)CH H)CH2CH3 (also known as sec-butanol, 2-butyl alcohol, or 2butanol) is a flammable, colorless liquid that is soluble in 12 parts water and completely miscible with polar organic solvent such as ethers and other alcohols. Figure 4 Structure of sec-butyl alcohol

Tert-Butanol, C 4H10O is a colorless liquid or white solid, depending on the ambient temperature. It is the simplest tertiary alcohol. and alcohol. and one of the four isomers of butanol. tert-Butanol butanol. tert-Butanol is a clear liquid with a camphor-like camphor- like odor. It is very soluble in water and miscible

above 25 °C. As a tertiary alcohol, tertbutanol is more stable to oxidation and less reactive than the other isomers of butanol. tert-Butanol is used as a solvent, as a denaturant for ethanol, as an ingredient in paint removers, removers, as an octane booster for gasoline, gasoline, as an oxygenate gasoline additive, additive, and as an intermediate in the synthesis of other chemical commodities, other flavors and perfumes. Figure 5 Structure of tert-butyl alcohol

Isopropyl alcohol (also propan-2ol, 2-propanol is a common name for a chemical compound with the molecular formula C3H8O. It is a colorless, flammable chemical compound with a strong odor. strong odor. It It is the simplest example of a secondary alcohol, alcohol, where the alcohol carbon is attached to two other carbons. Being a secondary alcohol, isopropyl alcohol can be oxidized to acetone, which is the corresponding ketone. Isopropyl alcohol dissolves a wide range of non-polar compounds. It is also relatively non-toxic and evaporates quickly. Thus it is used widely as a solvent and as a cleaning fluid,







Figure 7 Structure of Isopropyl alcohol

Benzyl alcohol, C 6H5CH2OH, is a colorless liquid with a mild pleasant aromatic odor. It is a useful solvent due to its polarity, low toxicity, and low vapor pressure. pressure. Benzyl alcohol is partially soluble in water (4 g/100 mL) and completely miscible in alcohols and diethyl ether. ether. Like most alcohols, it reacts with carboxylic acids to form esters. esters. Benzyl alcohol is used as a general solvent for inks, paints, lacquers, and lacquers, and epoxy resin coatings. It is also a precursor to a variety of esters, used in the soap, perfume, perfume, and flavor industries. industries. It is often added to intravenous medication solutions as a preservative due to its bacteriostatic its bacteriostatic and antipruritic properties.

of carboxylic acids, acids, esters, anhydrides, acyl halides, amides, and quinones, and it is the characteristic functional group of aldehydes and and ketones. ketones. Carboxylic acid (and their derivatives), aldehydes, ketones, and quinones are also known collectively as carbonyl compounds. Aldehydes Aldehydes and ketones ketones contain contain carbonyl carbonyl groups attached to alkyl or aryl groups and a hydrogen atom or both. These groups have little effect on the electron distribution in the carbonyl group; thus, the properties of aldehydes and ketones are determined by the behaviour of the carbonyl group. In carboxylic acids and their derivatives, the carbonyl group is attached to one of the halogen atoms or to groups containing atoms such as oxygen, nitrogen, or sulfur. These atoms do affect the carbonyl group, forming a new functional group with distinctive properties.

Figure 7 Structure of a Carbonylcontaining compound

Figure 6 Structure of Benzyl alcohol

An aldehyde is an organic compound containing a terminal carbonyl group. This functional group, called an aldehyde group, consists of a carbon atom bonded to a hydrogen







functional group is -CH=O, and the general formula for an aldehyde is RCH=O. The aldehyde group is occasionally called the formyl or methanoyl group. The word aldehyde is a combination of parts of the words alcohol and dehydrogenated, because the first aldehyde was prepared by removing two hydrogen atoms (dehydrogenation) from ethanol. Molecules that contain an aldehyde group can be converted to alcohols by the addition of two hydrogen atoms to the central carbon oxygen double bond (reduction). Organic acids are the result of the introduction of one oxygen atom to the carbonyl group (oxidation). Aldehydes Aldehydes are very easy to detect by smell. smell. Some are very fragrant, and others have a smell resembling that of rotten fruit. Figure 8 Structure of Aldehyde

Ketone features a carbonyl a carbonyl group (C=O) bonded to two other carbon atoms. They differ from aldehydes in that the carbonyl is placed between two carbons rather than at the end of a carbon skeleton. skeleton. They are also distinct from other functional groups, groups, such as

important physiological properties. They are found in several sugars and in compounds for medicinal use, including natural and synthetic steroid synthetic steroid hormones. Figure 9 Structure of Ketone

Some of the carbonyl-containing compounds used in the experiment are benzaldehyde, n-butraldehyde, acetaldehyde, acetone and acetophenone. Benzaldehyde, C 6H5CHO (also known as benzenecarbonal) is a colorless liquid aldehyde with a characteristic almond odor. It boils at 180°C, is soluble in ethanol, but is insoluble in water. It is formed by partial oxidation of benzyl alcohol, and on oxidation forms benzoic acid. It is called oil of bitter almond, since it is formed when amygdalin, a glucoside present in the kernels of bitter almonds and in apricot pits, is hydrolyzed, e.g., by crushing the kernels or pits and boiling them in water; glucose and hydrogen cyanide (a poisonous gas) are also formed. It is also prepared by oxidation of toluene or benzyl chloride or by treating benzal chloride with an alkali,







Figure 10 Structure of Benzaldehyde

acid, polyvinyl butyral, methyl amyl ketone). It is also used as an intermediate to make pharmaceuticals, agrochemicals, antioxidants, rubber accelerators, textile auxiliaries, perfumery and flavors. Figure 12 Structure of nButyraldehyde

Acetaldehyde, Acetaldehyde, CH 3CHO (also known as ethanol) is a colorless liquid aldehyde, aldehyde, sometimes simply called aldehyde. It is soluble in water and ethanol. Acetaldehyde is made commercially by the oxidation of ethylene with a palladium catalyst. It is used as a reducing agent (e.g., for silvering mirrors), in the manufacture of synthetic resins and dyestuffs, and as a preservative. Figure 11 Structure of Acetaldehyde

Acetone (also known as propanone) is the organic compound with the formula (CH3)2CO. This colorless, mobile, flammable liquid with a characteristic sweetish smell is the simplest example of the ketones. Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory. Figure 13 Structure of Acetone

N-butyraldehyde (also known as butanal) is an organic compound with the formula CH 3(CH2)2CHO. This compound is the aldehyde derivative of butane. butane. It is a colourless flammable liquid that smells like sweaty feet. It is miscible with most organic solvents. nButyraldehyde is used as an

Acetophenone Acetophenone is the organic compound with the formula C6H5C(O)CH 3. It is the simplest aromatic ketone. ketone. This colourless, viscous liquid is a precursor to useful









recovered as a by-product of the oxidation of ethylbenzene, ethylbenzene, which mainly gives ethylbenzene hydroperoxide for use in the production of propylene of propylene oxide

applicable only to alcohols that are soluble in the reagent. This limits the test in general to monofunctional alcohols lower than hexyl and certain polyfunctional molecules.

Figure 14 Structure of Acetophenone

Chromic Acid Test (Jones Oxidation) detects the presence of a hydroxyl substituent that is on a carbon bearing at least one hydrogen, and therefore oxidizable. The hydroxyl- and carbonylcontaining compounds were analyzed by utilization of different tests such as testing the solubility of alcohols in water, Lucas Test, Chromic Acid Test (Jones Oxidation), 2,4-Dinitrophenylhydrazone Test, Fehling’s Test, Tollens’ Silver Mirror Test, and Iodoform Test. Most organic compounds are not soluble in water with the exception of low molecular-weight amines and oxygen-containing compounds like alcohols, carboxylic acids, aldehydes, and ketones. Low molecular-weight compounds are generally limited to those with fewer than five carbon atoms.

2,4-Dinitrophenylhydrazone Test can be used to qualitatively detect the carbonyl functionality of a ketone or aldehyde functional group. Fehling’s Test and Tollens’ Silver Mirror Test are used to detect aldehydes. However, Fehling's solution can only be used to test for aliphatic aldehydes, whereas Tollens' reagent can be used to test for both aliphatic and aromatic aldehydes. Iodoform Test is a test for methyl carbinol (secondary alcohol with adjacent methyl group) and methyl







tube containing alcohol and the mixture was shaken thoroughly after each addition. If cloudiness resulted, 0.25-ml of water at a time was added continuously with vigorous shaking until a homogeneous dispersion results. The total volume of water added was noted. If cloudiness resulted after the addition of 2.0-ml of water, the alcohol is said to be soluble in water. The results were noted down. B. Lucas Test

1 drop of liquid or a small amount of the solid sample was dissolved in 1-ml of acetone in a small vial or test tube. 2 drops of 10% aqueous Potassium dichromate solution and 5 drops of sulphuric acid were added into the mixture. D. 2,4-dinitrophenylhydrazone (or 2,4DNP Test)

This test was performed on acetone, acetaldehyde, n-butyraldehyde, benzaldehyde, and acetophenone.

This test was performed on n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. Lucas reagent was prepared by dissolving 16 g of anhydrous zinc chloride in 10-ml of concentrated hydrochloric acid. The mixture was then allowed to cool.

The reagent was prepared by slowly adding a solution of 3 g of 2,4dinitrophenylhydrazine in 15-ml of concentrated sulphuric acid, while stirring to a mixture of 20-ml of water and 70-ml of 95% ethanol. The solution was then stirred and filtered.

Two to three drops of the sample were added to 1-ml of the reagent in a small vial or test tube and the mixture was shaken vigorously for a few seconds. The mixture was allowed to stand at

A drop of a liquid sample was placed into a small sample. 5 drops of 95% ethanol was added and well shaken. Afterwards, Afterwards, 3 drops of 2,4-DNP was added and if no yellow or orange







prepared by dissolving 7 g of hydrated copper (II) sulfate in 100-ml of water. Fehling’s B was prepared by mixing 35 g of Potassium sodium tartrate and 10 g of Sodium hydroxide in 100-ml water. 1-ml 1-ml of freshly prepared Fehling’s reagent was placed into each test tube. 3 drops of the sample to be tested was added in to the tube. The tubes were then placed in a beaker of boiling water and changes within 10-15 minutes were observed. F. Tollens’ Silver Mirror Test

This test was performed on acetaldehyde, benzaldehyde, acetone, n-butyraldehyde, and acetophenone. The reagent was prepared by adding 2 drops of 5% Sodium hydroxide solution to 2-ml of 5% Silver nitrate solution and mixing thoroughly. Next, only enough 2% ammonium hydroxide (concentrated ammonium hydroxide is 28%) was added drop by drop and with stirring to dissolve the precipitate. Adding excess

It was noted that if Tollens’ reagent is left unused for a period of time, it may form explosive silver. This was avoided by neutralizing unused reagent with a little nitric acid and discarded afterwards. G. Iodoform Test

This test was performed on acetaldehyde, acetone, acetophenone, benzaldehyde, and isopropyl alcohol. Two drops of each sample was placed into its own small vial or test tube. 20 drops of fresh chlorine bleach (5% Sodium hypochlorite) was slowly added while shaking to each test tube and then, mixed. The formation of a yellow participate was noted. Results and Discussion Table 1 Solubility of Alcohol in Water

Alcohol

Condensed Structural Formula

Amount of Water (in ml) needed to produce a

Solubility in Water







Table 1 shows alcohols such as ethanol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and benzyl alcohol and their solubility in water. Ethanol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol are all miscible with water with the exception of benzyl alcohol which exhibited insolubility. The table shows that all alcohols are soluble in water except under C 6. There are different factors affecting solubility. One of which is number of carbon atom wherein the higher the number of carbon atoms, the more insoluble the alcohol is in water. Another factor is the branching of carbon chain in which the more branching present, the more soluble (with the same number of carbons) it is. Lastly, the presence of polar functional groups (-OH, -NH2, CO2H) also tends to affect alcohol solubility in water. A compound with polar functional group is more soluble in water. As stated, all alcohols alcohols are soluble

sec-butyl alcohol, and n-butyl alcohol. Ethanol exhibits fastest solubility because it has only two carbon atoms as compared to the butanol derivatives having four carbon atoms. Tert-butyl alcohol is the most soluble among the butanol derivatives because it has the most branching substituents present. Table 2 Reaction of Sample Compounds to Lucas Test Substance


Reaction

Inference

n-butyl alcohol

CH3CH2CH2CH2OH

Clear solution

Miscible

Sec-butyl alcohol

Clear solution

Miscible

Tert-butyl alcohol

Formation of two layers with cloudy suspension

Immiscible

Table 2 shows the reaction of butanol derivatives to Lucas Test. Nbutyl alcohol and sec-butyl alcohol yielded a clear solution when subjected to Lucas Test whereas tert-butyl alcohol resulted to a cloudy immiscible suspension which eventually formed two layers.







on Table 2, tert-butyl alcohol immediately formed two layers; hence, it is known to be a tertiary alcohol. Secbutyl alcohol when subjected to Lucas test resulted to a clear solution although theoretically, a secondary alcohol dissolves to give a clear solution (provided R does not have too many carbon atoms in the chain.), then form chlorides (cloudy solution) within five minutes. N-butyl alcohol was unreactive and is considered to be the primary alcohol. Generally, the order of reactivity of the alcohols toward Lucas reagent is 3°>2°>1° because the reaction rate is much faster when the carbocation intermediate is more stabilized by a greater number of electron donating alkyl group bonded to the positive carbon atom. This means that the greater the alkyl groups present in a compound, the faster its reaction would be with the Lucas solution.

in the presence of zinc chloride at ordinary temperatures; chloride ion is too poor a nucleophilic agent to effect a concerted displacement reaction, on the one hand, and the primary carbonium ion is too unstable to serve as an intermediate in the carbonium mechanism, on the other. Hydrogen bromide and Hydrogen iodide, which have anions with nucleophilic reactivity increasing in that order, are increasingly reactive toward primary alcohols. These are nucleophilicity orders to be expected in hydroxylic solvents. Tertiary alcohols react with concentrated hydrochloric acid so rapidly that the alkyl halide is visible within a few minutes at room temperature, at first as a milky suspension and then as an oily layer. The acidity of the medium is increased by the addition of the anhydrous zinc chloride (a strong Lewis acid), and the reaction rate is increased further. This reaction is not a nucleophilic displacement comparable to that undergone by primary alcohols but









caused to separate by dilution of the mixture with ice water. Secondary alcohols are intermediate in reactivity between primary and tertiary alcohols. Although they are not appreciably affected by concentrated hydrochloric acid alone, they react with it fairly rapidly in the presence of anhydrous zinc chloride; a cloudy appearance of the mixture is observed within 5 minutes, and in about 10 minutes, a distinct layer is usually visible. Table 3 Reaction of Sample Compounds to Chromic Acid Test Substance n-butyl alcohol

Condensed Structural Formula CH3CH2CH2CH2OH

Reaction Blue-green Solution

Isopropyl Alcohol

Blue-green Solution

Chromic Acid Test/Dichromate Test/Jones Test is a test for oxidizables or any compounds that possess reducing property (has an alpha acidic hydrogen. Reagent used includes chromium trioxide and concentrated sulphuric acid. Table 3 shows the reaction of nbutyl alcohol, sec-butyl alcohol, tertbutyl alcohol, n-butyraldehyde, benzaldehyde, acetone, and acetophenone to Chromic Acid test. Nbutyl alcohol. N-butyl alcohol, Sec-butyl alcohol, tert-butyl alcohol, nbutyraldehyde, acetone and acetophenone resulted to a blue-green







alcohols and aldehydes will reduce the orange-red chromic acid/sulfuric acid reagent to an opaque green or blue suspension of Cr(III) salts in 2-5 seconds. A primary alcohol reacts with chromic acid to yield aldehyde, which is further oxidized to carboxylic acid. A secondary alcohol reacts with chromic acid to yield ketone, which does not oxidize further. A tertiary alcohol is usually unreactive. Table 4 Reaction of Sample Compounds to 2,4-DNP Test Substance

Acetaldehyde

n-butyraldehyde


(conjugated carbonyl compounds) or yellow precipitate (non-conjugated carbonyl compounds). Table 4 shows the reaction of acetaldehyde, n-butyraldehyde, benzaldehyde, acetone, and acetophenone to 2,4-DNP test. All the samples exhibited positive result because they all formed either a yellow or an orange precipitate. Hence, 2,4DNP test proved that the samples are carbonyl-containing compounds and are either aldehydes or ketones.

Reaction Yellow precipitate

Yellow solution

The reaction of 2,4-DNPH with







different from that of 2,4o dinitrophenylhydrazine (MP 198 C). If necessary, this hydrazone derivative can be recrystallized from a solvent such as ethanol. Solvents containing reactive carbonyl groups should not be used, as they may result to formation of another hydrazone. The color of a 2,4dinitrophenylhydrazone may give an indication as to the structure of the aldehyde or ketone from which it is derived. Dinitrophenylhydrazones of aldehydes or ketones in which the carbonyl group is not conjugated with another functional group are yellow. Conjugation with a carbon-carbon double bond or with a benzene ring shifts the absorption maximum towards the visible and is easily detected by an

Benzaldehyde

No Decolorization

Acetone No Decolorization

acetophenone

No Decolorization

Fehling’s Test is a test for aldehydes. Reagents include CuSO4, NaOH ( Cu 2+ in alkaline solution). Positive result is the formation of brickred precipitate. As shown in Table 5, acetaldehyde and n-butyraldehyde exhibited positive result. Acetaldehyde, in particular turned from blue to muddy green then formed a brick-red







n-butyraldehyde

Silver Mirror

Table 7 Reaction of Sample Compounds to Iodoform Test

Substance Benzaldehyde

Silver Mirror Acetaldehyde


Reaction

Yellow precipitate

Acetone Black Solution

acetophenone

Black Solution

Tollens’ Silver Mirror test is a test for aldehydes. The preparation of Tollens reagent is based on the formation of a silver diamine complex that is water soluble in basic solution. As shown in Table 6, acetaldehyde, nbutyraldehyde, and benzaldehyde exhibited positive result of formation of

Benzaldehyde

BrownishRed Oily Droplet

Yellow precipitate

Acetone

acetophenone

Yellow precipitate

Isopropyl alcohol

Yellow precipitate

Iodoform Test is a test for methyl







When a - methyl carbonyl compounds react with iodine in the presence of a base, the hydrogen atoms on the carbon adjacent to the carbonyl group (a hydrogens) are subsituted by iodine to form tri iodo methyl carbonyl compounds which react with OH - to produce iodoform and carboxylic acid (2):

References BOOKS: Bayquen, A., Sarile, A. et al. (2014). Laboratory Manual In Organic Chemistry. Quezon City,

Aldehyde. (2010). In Encyclopædia Britannica. Retrieved October 19, 2014, from Encyclopædia Britannica Online: http://www.britannica.com/EB http://www.britannica.com/EBchecked/topic/ checked/topic/13527/ald 13527/ald ehyde. Aldehydes. Retrieved October 19, 2014 from http://science.jrank.org/pages/ http://science.jrank.org/pages/198/Aldehydes.ht 198/Aldehydes.html. ml. Benzaldehyde. Retrieved October 19, 2014 from http://www.encyclopedia.com/t http://www.encyclopedia.com/topic/benzaldehyde. opic/benzaldehyde.asp asp x.

Experiment 9 Formal Report on Classification test of hydroxyl-containing and carbonyl-containing organic compounds

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