Systematic Characterization of Oxygen-bearing Organic Compounds

Systematic Characterization of Oxygen-Bearing Organic Compounds Quintero, Christian Paul D., Ramos, Jandra Natanie C., Rapacon*, Mark Giane Dave V., Recto, Chris Vincent A. College of Science, University of Santo Tomas, Manila, Philippines __________________________________________________________________________________________

Abstract Qualitative Chemical Analysis makes use of qualitative data for interpretation of compound identity. The reference oxygen-bearing compounds—n-propanol, 2-propanol, t-butanol, formaldehyde and acetone— were subjected to the different classification tests. Positive results for Dichromate test classified npropanol, 2-propanol and formaldehyde as reducing agents; the Tollen’s test showed high specificity to formaldehyde; the Lucas test classified n-propanol, 2-propanol and t-butanol based on their reaction rates, with t-butanol being the most reactive; the DNPH test detected the carbonyl groups from formaldehyde and acetone; and the Iodoform test identified the oxidation of 2-propanol and acetone. Identification of two unknown oxygen-bearing compounds was based from the reactions of the reference standards. The functional class of Unknown A was known to be a secondary alcohol, while Unknown B was identified to be an aldehyde.

I. Introduction Oxygen-bearing compounds, from the name itself, are organic compounds that contain one or more oxygen. The known oxygen-bearing organic compounds are alcohol, phenol, ether, aldehyde, ketone, carboxylic acid, ester, and an anhydride (Solomons, Fryhle & Snyder, 2014). An alcohol is an organic compound with hydroxyl (— OH) group as its characteristic functional group. The

hydroxyl group is attached to an sp 3-hybridized carbon atom. Alcohols could be classified as primary (1O), secondary (2O), or tertiary (3O) alcohol. A primary (1O) alcohol is an alcohol whose hydroxyl group is attached to a primary carbon, a carbon that has only one other carbon attached to it (Solomons, Fryhle & Snyder, 2014). A 1O alcohol of particular interest in the experiment is n-Propanol (CH3CH2CH2OH) (Fig.1). The IUPAC name for nPropanol is 1-Propanol. It is a colorless liquid, with molar mass of 60.09 g/mol, and a polar solvent. It is used as a cleaning

fluid,

adhesive

and

stain

remover, and

as

preservative (Pavia, 2007). A secondary (2O) alcohol is an alcohol whose hydroxyl group is attached to a secondary carbon, a carbon that bears two other carbon atoms (Solomons, Fryhle & Snyder, 2014). A

2O

alcohol

of

particular

interest

is

2-Propanol

(CH3CH(OH)CH3) (Fig. 2). It is commonly known as isopropyl alcohol. Isopropyl alcohol is colorless, flammable chemical compound with a strong odor, has a molar mass of 60.1 g/mol and a boiling point of 82.6

O

C. It is typically

commercialized as antiseptic (Pavia, 2007). A tertiary (3O) alcohol is an alcohol whose hydroxyl group is attached to a tertiary carbon, a carbon that bears three other carbon atoms (Solomons, Fryhle & Snyder, 2014).

A 3O alcohol of particular interest in the experiment is t-butanol ((CH3)3COH) (Fig. 3). With its IUPAC name 2-methyl-2-propanol,

and

Figure commonly called tert-butyl alcohol, it is a clear liquid (or a colorless solid,10. depending on Anhydride Example

the ambient temperature) with a camphor-like odor. It has a molar mass of 74.12 g/mol and

a

boiling

point

ethanol denaturant, paint

of

83

O

C.

tert-Butyl

remover ingredient,

alcohol and

is

gasoline

used

as

a

solvent,

octane booster

and

oxygenate (Pavia, 2007). Phenol (Fig.4) is an alcohol whose hydroxyl group is attached to a benzene ring. However, they differ from simple alcohols with their relative acidity, separating them as distinct functional group. Ethers (Fig.5) have the general formula R—O—R or R—O— R’, where R’ could be an alkyl (or phenyl) group different from R (Solomons, Fryhle & Snyder, 2014). Moreover, aldehyde is a functional group that contains a carbonyl group(C=O). The carbonyl group of an aldehyde is bonded to one hydrogen and one carbon atom. One exception, and is of particular interest, is the formaldehyde (CH 2O) (Fig. 6) which is the only aldehyde bearing two hydrogen atoms (Solomons, Fryhle & Snyder, 2014). Commonly known as formalin, it is gas at room temperature, colorless and has a characteristic pungent, irritating odor. It has a molar mass of 30.031 g/mol and a boiling point of -19 OC. It is commonly used in embalming, as nail hardener or nail varnish (Pavia, 2007). Another organic compound are the ketones; like aldeydes, ketones also contain carbonyl group. However, the carbonyl group in ketones is bonded to two carbon atoms (Solomons, Fryhle & Snyder, 2014). A ketone of particular interest is acetone

((CH3)2CO) (Fig. 7). Its IUPAC name is 2-propanone; it is the simplest ketone. Being a polar solvent, it is colorless, volatile, flammable liquid. It has a molar mass of 58.08 g/mol and a boiling point of 56 OC. Acetone is used as active ingredient in nail polish remover and as paint thinner (Pavia, 2007). In addition, carboxylic acids(Fig.8) have a carbonyl group bonded to a hydroxyl group (RCO2H). Esters(Fig.9), on the other hand, have a carbonyl group bonded to an alkoxyl (—OR) group (RCO2R’). Lastly, organic acid anhydride (Fig.10) is a compound that has two acyl (R bonded to carbonyl) groups bonded to the same oxygen atom (Solomons, Fryhle & Snyder, 2014). The systematic characterization of organic compounds is known as qualitative organic analysis, which chemists often shorten to “qual organic.” Qual organic is typically used to identify a compound that has been obtained by a process whose outcome is uncertain, or from a natural product or other source whose composition is unknown (Lehman, 2010). Five classification tests were used in the course of experiment. Thus, five reference standard organic compounds were used: three alcohols, aldehyde, and a ketone. The first chemical test was Dichromate Test. Dichromate Test, also known as Jones Oxidation Test, is mainly used to distinguish between primary, secondary, and a tertiary alcohol based on their oxidation reactions. It is a functional-class test for alcohols and aldehydes. Positive visible result is the presence of intense blue-green solution (Pavia, Lampman, Kriz, & Engel, A microscale laboratory techniques, 2013).

approach

to

organic

The second test is Tollen’s Test. It is also called “Silver-Mirror Test.” It is used to distinguish between an aldehyde and a ketone, a functional class test for aldehydes based on their oxidation reactions. Positive visible result is the formation of silver-mirror coating in the test tube (Pavia, Lampman, Kriz, & Engel, A microscale

approach to

organic laboratory techniques, 2013). Thirdly, the Lucas Test is used to classify alcohols in accordance with their reactivity. It is both a functional-class test and chemical test that provides structural information of alcohols. Positive Visible result yields a turbid solution (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013). The

fourth

test

is

DNPH

Test.

This

test

is

further

called

2,4-

dinitrophenylhydrazine test. This chemical test is used to detect the carbonyl group functionality in aldehydes and ketones basing from condensation reaction; therefore, it is a functional-class test for aldehydes and ketones. Positive visible result yields to formation of red-orange precipitate (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013). Lastly, the Iodoform Test is mainly used to identify methyl ketones. This test provides structural information not only for ketones, but also for alcohols basing from the oxidation reactions. Positive visible result yields a yellow precipitate (Pavia, Lampman, Kriz, & Engel, A microscale approach to organic laboratory techniques, 2013). In this experiment, the different structural features of oxygen-bearing compounds were identified. Qualitative chemical analyses characterized the identity of each oxygenbearing organic compounds based from their chemical reactions. Also, the structural

feature and identity of an unknown compound was deduced. Lastly, chemical equations involved in each test were derived.

II. Methodology The materials needed were prepared first. Twenty-six small-sized (13x100 mm) test tubes were first prepared. The following reagents were procured from the laboratory technician: 10% potassium dichromate (10% K 2Cr2O7), 6M sulfuric acid (6M H 2SO4), Tollen’s Reagent, concentrated hydrochloric acid (HCl), anhydrous zinc chloride (ZnCl 2), DNPH Reagent, 10% potassium iodide (10% KI), and 5% aqueous sodium hypochlorite (5% NaClO). Alongside with the reagents were the reference standards—formaldehyde, acetone, n-Propanol, 2-Propanol, t-butanol—and the two unknown sample compounds, A and B. Parallel chemical testing was followed all throughout the whole experiment. Five chemical tests were conducted: Dichromate Test The reference standards and samples used were n-propanol, 2-propanol, tbutanol, formaldehyde, acetone, and the two unknown samples. Eight drops of the standards and the samples were placed and mixed with two drops of 10% K 2Cr2O7 and five drops 6M H2SO4 in separate test tubes assigned for each substance. The results were observed and recorded. Tollen’s Test The reference standards and samples used were formaldehyde, acetone, and the two unknown samples. Ten drops of the standards and the samples were placed

and mixed with 40 drops (2 mL) of Tollen’s Reagent. The chemical reactions were timed five minutes. The results were observed and recorded. Lucas Test The reference standards and samples used were n-propanol, 2-propanol, tbutanol, and the two unknown samples. Ten drops of the standards and the samples were placed and mixed with 20 drops of concentrated HCl in separate test tubes assigned for each substance. The test tubes were shaken well and turbidity was observed. If no turbid solution was observed, anhydrous ZnCl 2 was added. The results were observed and recorded. DNPH Test The reference standards and samples used were t-butanol, formaldehyde, acetone, and the two unknown samples. Ten drops of the standards and the samples were placed and mixed with 20 drops of DNPH Reagent in separate test tubes assigned for each substance. The results were observed and recorded. Iodoform Test The reference standards and samples used were 2-propanol, t-butanol, , acetone, and the two unknown samples. Ten drops of the standards and the samples were placed and mixed with 20 drops of 10% KI and 20 drops 5% NaClO (aq) in separate test tubes assigned for each substance. The results were observed and recorded.

III. Results and Discussion Table 1. Data of Results of the Chemical Tests for the Reference Standards. The gray cells indicate that standards were not subjected to a particular test.

Standards

n-propanol

2-propanol

Dichromate Test

Tollen’s Test

Blue-green solution (+)

Chemical Tests Lucas Test Before After DNPH Test adding adding ZnCl2 ZnCl2 Clear Clear solution solution

Iodoform Test

(-)

Blue-green solution (+)

Clear solution

Yellowish white precipitate turned to yellow

Slightly turbid

(+)

(+)

t-butanol

Formaldehyde

Acetone

Orange solution

Turbid Solution

(-)

Turbid Solution

(+)

Orange solution, Precipitate absent

(-)

Silver-mirror precipitate formed

Yellow precipitate formed

Orange solution

Clear Solution

(-)

(-)

Orange precipitate formed

Blue-green solution

(+)

(+)

Yellow solution

(-)

(+)

(+)

Yellow precipitate formed

(+)

Table 2. Data of Results of the Chemical Tests for the Unknown Samples.

Standards

Unknown A

Unknown B

Dichromate Test

Tollen’s Test

Blue-green solution (+)

Clear Solution

Blue-green solution (+)

(-)

Silver-mirror precipitate formed

(+)

Chemical Tests Lucas Test Before After DNPH Test adding adding ZnCl2 ZnCl2 Yellow solution, Clear Slightly Precipitate solution turbid absent

(-)

Clear solution

Clear solution

Yellow precipitate formed

(+)

Iodoform Test Yellowishwhite precipitate formed

(+)

Red-orange solution

(-)

Table 1shows the results of the following chemical reactions on the reference standards. For the dichromate test (Jones Oxidation Test), n-propanol, 2-propanol, and the formaldehyde resulted positive for the test (formation of blue-green solution). Since n-propanol is a primary alcohol, the reaction of the standard with K 2Cr2O7 and H2SO4 produces this balanced chemical equation: 20 CH3CH2CH2OH+ 6 K2Cr2O7 + 24 H2SO4  6 Cr2(SO4)3 + 6 K2SO2 + 15 CH3CH2CH2COOH + 44 H2O The reaction between n-propanol being a primary alcohol with the two other reactants yields the formation of butanoic/butyric acid (CH 3CH2CH2COOH) which is a carboxylic acid. A 1O alcohol oxidizes first to an aldehyde (partial oxidation), which is further oxidized into a carboxylic acid—butanoic acid in this case. The partial oxidation to aldehyde does not take so long because the oxygen from the dichromate easily further oxidizes the aldehyde, specifically the hydrogen attached to the carbonyl group of the aldehyde. The full oxidation to a carboxylic acid takes place. The intense bluegreen color of the solution is due to the presence of Chromium (III) Sulfate (Cr 2(SO4)3) which is an essential product in the reaction. It gives the solution the distinctive bluegreen color. The chromium is oxidized from a +3 state (orange solution) to a +6 state (blue-green solution) (Shriner, Fuson, Curtin, Hermann &Morrill, 1997). The reaction of 2-propanol, on the other hand, produces this balanced chemical equation: 3 CH3CHOHCH3 + K2Cr2O7 + 4 H2SO4  3 CH3COCH3 + Cr2(SO4)3 + 7 H2O + K2SO4 A 2O alcohol, like 2-propanol, that reacts with K 2Cr2O7 and H2SO4 yields the formation of acetone (CH3COCH3) which is a ketone, and also the chromium (III) sulfate

(Cr2(SO4)3). Again, the blue-green color is due to the presence of the Cr 2(SO4)3 as a product of oxidation from Cr3+ to Cr6+. However, once the 2-propanol was oxidized to acetone, no further oxidation reaction happens. The reason behind this is the absence of terminal hydrogen attached directly to the carbonyl group (which is present on aldehydes). In aldehydes, further oxidation happens because the hydrogen attached to the carbonyl could be easily oxidized, rendering the compound a great reducing agent. With the absence of that hydrogen in the acetone (ketone), therefore it could not be further oxidized (Lehman, 2010). Also, the reaction of the formaldehyde produces this balanced chemical equation: 3CH3OH + 2K2Cr2O7 + 8H2SO4 = 3HCOOH + 2K2SO4 + 2Cr2(SO4)3 + 11H2O Again, oxidation of an aldehyde is favored because of the presence of the hydrogen attached to the carbonyl group. In the case of formaldehyde, the R group is also hydrogen, which means that two hydrogens are attached to carbonyl group, thus, it is easily oxidized into a formic acid (HCOOH) which is a carboxylic acid. Aliphatic aldehydes react more quickly than aromatic aldehydes. Aldehydes, however, react more slowly than alcohols. The blue-green coloration is due to the presence of Cr2(SO4)3 as one of the products (Lehman, 2010). The orange solution as a negative result for both t-butanol and acetone is because of the potassium dichromate (K2Cr2O7), which is an orange solution. It was already stated that ketones do not undergo oxidation to lack of hydrogen to be oxidized. Thus, the color of the oxidizing reagent is retained due absence of oxidation reaction.

However, for a 3O alcohol like t-butanol, oxidation is not possible because oxidation only happens when the oxidizing agent removes the hydrogen from the hydroxyl group, and the hydrogen attached to the carbon where the hydroxyl group is attached. In the case of t-butanol, a tertiary carbon does not have any hydrogen bonded to it, thus, oxidation could not proceed (Shriner, Fuson, Curtin, Hermann &Morrill, 1997). Tollen’s Test is a more specific classification test; it is highly specific to aldehydes. The formaldehyde resulted positive in this test. The reaction produces this balanced chemical equation: HCOH + 2Ag(NH3)2OH  2Ag + HCOONH4 + H2O + 3NH3 Most aldehydes reduce ammoniacal silver nitrate solution to give a precipitate of silver metal. As the formaldehyde, an aldehyde, is oxidized to an acid, the silver is reduced from a +1 oxidation state of the diamminesilver(I) ion (Ag(NH 3)2+) to elemental silver (Ag) and is deposited as a silver mirror or colloidal silver inside the test tube. The Tollen’s reagent (Ag(NH3)2OH) oxidizes the formaldehyde to ammonium formate (HCOONH4) which is an ammonium salt of carboxylic acid (formic acid). The presence of the hydrogen atoms bonded to carbonyl group make aldehydes very easy to oxidize, and act as strong reducing agents (Pavia, Lampman, Kriz & Engel, Introduction to organic laboratory techniques: A microscale approach, 1995). The acetone resulted negative because ketones, like acetone, do not have that particular hydrogen atom; they are resistant to oxidation. Only very strong oxidizing agents like potassium manganate (VII) solution (potassium permanganate solution) oxidize ketones. However, they do it in a destructive way, breaking carbon-carbon

bonds. However, certain ketones such as α-alkoxy- or α-dialkylaminoketone result positive in this test (Pavia, Lampman, Kriz & Engel, Introduction to organic laboratory techniques: A microscale approach, 1995). Under the Lucas Test, only the t-butanol and

the

2-propanol

produced turbid (slightly turbid

for

the

latter)

Figure 11. SN1

solution among the three alcohols. The mechanism involved in this test is an SN 1 Nucleophilic Substituion Reaction (Fig.11). Zinc chloride (ZnCl2) is attracted to the electrons of the oxygen (hydroxyl group). The leaving group, the alcohol-zinc chloride complex, departs from the alkyl group because the positive charge of the oxygen that was formed weakens the C—O bond. Thus, a carbocation is formed. However, the chloride ion (Cl-) from the hydrochloric acid (HCl) acts as the nucleophile and forms a bond with the carbocation. Thus, an alkyl-chloride is produced. In addition, ZnCl 2 is a catalyst for this reaction. The resultant alkyl chloride is insoluble in water and separates from the Lucas reagent (ZnCl2 in concentrated HCl), forming a cloudy mixture (Lehman, 2010). The reaction for t-butanol in this test is (CH3)3COH + HCl

ZnCl

2

(CH3)3CCl + H2O

Tertiary alcohols, like t-butanol, are soluble in the Lucas reagent and should turn the reagent cloudy almost immediately and soon form a separate layer of alkyl chloride

2-chloro-2-methylpropane ((CH3)3CCl). The acidity of the medium is increased by the addition of the anhydrous ZnCl 2, which is a strong Lewis acid, and as a result, the reaction rate is increased. The high reactivity of t-butanol is a consequence of the relatively great stability of the intermediate carbocation; 3 O carbocation is the most stable carbocation (Shriner, Fuson, Curtin, Hermann &Morrill, 1997). The reaction for 2-propanol in this test is CH3CH(OH)CH3 + HCl

ZnCl

2

CH3CH(Cl)CH3 + H2O

Secondary alcohols are intermediate in reactivity between primary and tertiary alcohols. Although they are not appreciably affected by concentrated HCl alone, they react with it fairly rapidly in the presence of anhydrous ZnCl 2. Also, the intermediate carbocation formed in the reaction is secondary (2 O) carbocation, which is less stable than 3O carbocation, but more stable than the primary (1 O) carbocation. That is the reason why the solution turned a slightly turbid (Lehman, 2010). Primary alcohol such as n-propanol did not react perceptibly with HCl even in the presence of ZnCl2 at ordinary temperatures. Chloride ion (Cl -) is too poor to be a nucleophilic agent to effect a concerted displacement reaction, and additionally, the 1 O carbocation is too unstable to serve as an intermediate in the SN 1 mechanism. Also, npropanol is insoluble in Lucas reagent that is why no reaction occurred (Shriner, Fuson, Curtin, Hermann &Morrill, 1997). The DNPH (2,4-Dinitrophenylhydrazine) Test resulted positive for formaldehyde and ketone. The DNPH test simply tests condensation reaction, where DNPH condenses with

carbonyl-containing molecules specifically the aldehydes and ketones (Pavia, Lampman, Kriz & Engel, A microscale approach to organic laboratory techniques, 2013). For

the

formaldehyde

and

acetone,

the

condensation reactions take place: HCOH + 2,4-dinitrophenylhydrazine

H SO 2 4

(alcohol)

following Figure 12. 2,4dinitrophenylhydraz ine (DNPH)

Formaldehyde-2,4-dinitrophenylhydrazone

Figure 13. Formaldehyde-2,4dinitrophenylhydraz one

CH3COCH3 + 2,4-dinitrophenylhydrazine

H SO (alcohol) 2 4

Acetone -2,4-dinitrophenylhydrazone

Dinitrophenylhydrazones are insoluble in water.

Figure 14. Acetone-2,4dinitrophenylhydraz one

The

precipitate may be oily at first and become crystalline on standing. The color of 2,4dinitrophenylhydrazone gives an indication as to the structure of the aldehyde or ketone from which it is derived. The color of the 2,4-dinitrophenylhydrazone (precipitate) formed is often a guide to the amount of conjugation in the original aldehyde or ketone. Unconjugated dinitrophenylhydrazones (carbonyl group is not conjugated with another

functional group) give yellow precipitates, whereas conjugated dinitrophenylhydrazones (carbonyl with a C=C or a benzene ring) give orange to red precipitates. Compounds that

are

highly

conjugated

give

red

precipitates.

However,

the

2,4-

dinitrophenylhydrazine reagent is itself orange-red, and the color of any precipitate must be judged cautiously. Occasionally, compounds that are either strongly basic or strongly acidic precipitate the unreacted reagent (Lehman, 2010). Tert-butanol does not yield any positive result because primarily, it does not contain any carbonyl group. There is a need for a carbony group in the substrate since this carbony group will be condensed by the DNPH and produces the distinct part of the 2,4-dinitrophenylhydrazones. Also, the 2,4-dinitrophenylhydrazone gives the orange-red color that precipitates from the solution (Shriner, Fuson, Curtin, Hermann &Morrill, 1997). The last test would be the Iodoform Test. It detects the —CH(OH)CH 3 and the — COCH3

groupings. Only 2-propanol and acetone resulted positive. The following

reactions contribute to the positive results of the two compounds: CH3CH(OH)CH3 + I2 + 2 NaOH CH3COCH3 + 2 NaI + 2 H2O CH3COCH3 + 3 I2 + 3 NaOH  CH3COCI3 + 3NaI + 3H2O CH3COCI3 + NaOH  CH3COO- Na+ + CHI3 (s) In the experiment, potassium iodide (KI) and Sodium hypochlorite (NaClO) are used as reagents, in substitute with iodine and sodium hydroxide. However, it still follows the same mechanism. The alcohol, 2-propanol (CH3CH(OH)CH3), is oxidized to acetone (CH3COCH3), a methyl ketone, by the iodine bleach.

In the reactions above, the iodine reacts with the sodium hydroxide to produce sodium iodate(I). This is an oxidizing agent (Pavia, Lampman, Kriz & Engel, Introduction to organic laboratory techniques: A microscale approach, 1995). In the experiment, the sodium hypochlorite (NaClO) acts as the oxidizing agent. The sodium chlorate (I) solution is an oxidizing agent, and oxidizes the iodide ions in the potassium iodide to iodine. As well as any possible precipitate, the typical reddish-brown colour of iodine solution being formed during the reaction is present (Pavia, Lampman, Kriz & Engel, A microscale approach to organic laboratory techniques, 2013). Iodination occurs preferentially and completely on the methyl group of the acetone. Cleavage and oxidation of the triiodo intermediate (CH3COCI3) produces the sodium acetate (CH3COO- Na+), the sodium salt of acetic acid and iodoform (CHI3) in the form of yellow solid. The test is positive for acetaldehyde, methyl ketones such as the acetone, and methyl carbinols (alcohols that contain a —CH(OH)CH 3 grouping) (Pavia, Lampman, Kriz & Engel, Introduction to organic laboratory techniques: A microscale approach, 1995). In addition to the proof that using sodium hypochlorite will still follow the same mechanism, sodium hypochlorite solution is alkaline and contains enough hydroxide ions to carry out the second half of the reaction. Sodium hypochlorite is alkaline because it reacts reversibly with water to form the weak acid chloric (I) acid together with hydroxide ions (Lehman, 2010). The established reaction mechanisms of the reference standards will help a person identify and classify a certain unknown organic compound. Table 2 shows the results of the different chemical tests the two unknown sample have undergone through.

Unknown A resulted positive for dichromate test; therefore, it could not be a ketone or a tertiary alcohol. It means that it could be oxidized. Yet, a negative result for Tollen’s test will deductively lead to either a primary or a secondary alcohol as the only possible choices. The result suggests that it is not an aldehyde, thus, an alcohol. The results from the Lucas and iodoform test confirms that the unknown A is actually a secondary alcohol because a) Secondary alcohols could still undergo nucleophilic substitution but slightly slower in reaction rate compared to tertiary alcohols and b) Only secondary alcohols and methyl ketones yield positive results for iodoform test. Thus, unknown A is a ketone. For the unknown B, since it yielded positive for the dichromate test, the possible choices could only be a primary and secondary alcohol or an aldehyde and could be oxidized. The Tollen’s test suggests that since it is positive, it must be an aldehyde. The results from DNPH and iodoform tests confirm the result because a) It is a carbonylcontaing compound and b) It could not form the iodoform. Therefore, unknown B must be an aldehyde. Qualitative Organic Analysis is an essential systematic procedure for the identification of many unknown organic compounds. Results from the chemical tests could be used to identify not only the functional-class of the compound, but may also provide structural information about the compounds.

IV. Conclusion The characterization of the oxygen-bearing reference standards n-propanol (primary alcohol), 2-propanol (secondary alcohol), t-butanol

(tertiary alcohol),

formaldehyde (aldehyde) and acetone (ketone) could be done using the qualitative

organic classification tests: Dichromate Test, Tollen’s Test, Lucas Test, DNPH Test and Iodoform Test. The dichromate test classified n-propanol, 2-propanol and formaldehyde as

reducing

agents

(oxidized);

the

Tollen’s

test

identified

carbonyl-containg

formaldehyde; the Lucas test classified n-propanol, 2-propanol and t-butanol based on their reaction rates; the DNPH test detected the carbonyl groups from formaldehyde and acetone; and the Iodoform test identified the oxidation of 2-propanol and acetone. The functional-class of the two unknown organic compounds—Unknown A and Unknown B —were identified to be a secondary alcohol and aldehyde, respectively. V. References Lehman, J. W. (2010). Multiscale operational organic chemistry: A problem-solving approach to the laboratory course (2nd ed.). Upper Saddle River, NJ: Pearson

Prentice Hall.

Pavia, D. L. (2007). Introduction to organic laboratory techniques: A microscale approach. Belmont, CA: Thomson Brooks/Cole. Pavia, D. L., Lampman, G. M., Kriz, G. S., & Engel, R. G. (1995). Introduction to organic laboratory techniques: A microscale approach (2nd ed.). Orlando, FLO: Saunders College Publishing. Pavia, D. L., Lampman, G. M., Kriz, G. S., & Engel, R. G. (2013). A microscale approach to organic laboratory techniques (5th ed.). Belmont, CA: Brooks/Cole,

Cengage Learning.

Shriner, R. L., Fuson, R. C., Curtin, D. Y., Hermann, C. K., & T. C., Morrill. (1997). The systematic identification of organic compounds (7th ed.). New York: John Wiley &

Sons.

Solomons, T. G., Fryhle, C. B., & Snyder, S. A. (2014). Organic Chemistry International Student Version (11th ed.). Singapore: John Wiley & Sons Singapore Pte. Ltd.