Analysis of Oxygen-Bearing Organic Compounds

[pic 1][pic 2]

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 n-propanol, 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). [pic 3]

An alcohol is an organic compound with hydroxyl (—OH) group as its characteristic functional group. The hydroxyl group is attached to an sp3-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 n-Propanol 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).[pic 4]

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 OC. It is typically commercialized as antiseptic (Pavia, 2007). [pic 5]

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 commonly called tert-butyl alcohol, it is a clear liquid (or a colorless solid, depending on the ambient temperature) with a camphor-like odor. It has a molar mass of 74.12 g/mol and a boiling point of 83 OC. tert-Butyl alcohol is used as a solvent, ethanol denaturant, paint remover ingredient, and gasoline octane booster and oxygenate (Pavia, 2007). [pic 6][pic 7][pic 8]

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 (CH2O) (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).