FUNCTIONAL GROUPS: Carboxylic Acid

4 | Page

Carboxylic AcidPrepared by: Emmanuel C. RevillaREPORTER: Emmanuel C. RevillaPHYSCI M15: BIOLOGICAL CHEMISTRYMrs. Clarissa F. Gregana

1 | Page

CARBOXYLIC ACIDINTRODUCTIONCarboxylic acids are a large group of chemical compounds that all have a certain structure in common, composed of the three most important elements on earth carbon, oxygen and hydrogen. These various compounds make up the most abundant, naturally occurring organic acids. The slightly stinging sourness of citrus fruits, such as lemons, comes from one example called citric acid. Most of the compounds are relatively simple chemically, and as an acid, quite weak. They readily dissolve into individual molecules in solvents, including water. Even the most complex and stubborn of them are usually soluble in an alcohol solution.

Not only are they valuable in themselves, they also serve as starting materials for preparing numerous acyl derivatives such as acid chlorides, esters, amides, and thioesters.

STRUCTURE AND PROPERTIESCarboxylic acid are organic compounds containing a carboxyl group.

* A carboxyl group is a carbonyl group (C=O) with a hydroxyl group (OH) bonded to the carbonyl carbon atom.

BOILING & MELTING POINTCarboxylic acids are polar compounds because they possess a polar carbonyl group. (dipole-dipole interactions)Carboxylic acids also exhibit intermolecular hydrogen bonding since they possess a hydrogen atom bonded to an electronegative oxygen atom.

They have the highest boiling and melting points among all known functional groups/organic compounds.

SOLUBILITY IN WATERCarboxylic acids form hydrogen bonds with many water molecules. With 1-4 carbon atoms, they are soluble in water. ACIDITYThe most obvious property is implied by their name: carboxylic acids are acidic.They are the most acidic class of compounds that contain only carbon, hydrogen, and oxygen.Unsubstituted saturated monocarboxylic acids containing up to nine carbon atoms are liquids that have strong, sharp odors. Acids with 10 or more carbon atoms in an unbranched chain are waxy solids that are odorless (because of low volatility). Aromatic carboxylic acids, as well as dicarboxylic acids, are also odorless solids.

PREPARATION OF CARBOXYLIC ACIDSMany of the chemical reactions used for their preparation are oxidations.

MODERN APPLICATION/USE OF CARBOXYLIC ACID

Carboxylic acids are widely found in nature. You can find them as free acids like citric acid, tannic acid and malic acid. Esters the products of acids and alcohols also contain carboxylic acids. These include fats and oils, flavors of fruits and odors of flowers. Some bacteria can also cause natural reactions in which these acids are formed. Some examples include acetic acid from wine or cider, lactic acid found in sour milk and the butyric acid in rancid butter.Acetic AcidThis acid is found in vinegar and is responsible for giving it the sour taste. Vinegar means sour wine. It was discovered when bacteria reacted with wine and turned it sour. It is one of the simplest of carboxylic acids.

Tannic AcidYou may have heard of this acid, it has been used for tanning. You will find it in the bark of a number of trees. Tannic acid can be found as a yellow or light brown powder, which is highly soluble in water. It is used for the staining of wood and is also used when dyeing cotton.

Salicylic AcidThis acid is derived from the bark of the willow tree. Salicylic acid is used in acne creams to help reduce acne. It derives its name from the word Salix, which is Latin for Willow. Today this acid is used as a food preservative.

Citric AcidThis acid is found in most citrus fruits. It gives the tangy taste to lemons, limes, grape fruits and oranges. Citric acid is a natural preservative and used in both foods and soft drinks. It is also used in some bathroom and kitchen cleaning solutions.

Malic AcidThis acid is found in many unripe fruits like green apples. Malic acid includes green apples, plums, currants (seedless raisins) and a variety of other fruits.

Oxalic AcidThis acid was originally derived from the wood sorrel plant Oxalis. It is now made artificially and is used in bleaching and cleansing solutions.

Amino acidsThis acids are also among natures most important carboxylic acids. They are nicknamed the building blocks of proteins. Proteins, in turn, create the nearly infinite diversity of organic tissues, from hair, skin, heart to tree bark. Scientists have taken this cue, to utilize the acids in, or chemically covert them into, a vast variety of applications. Perfumes, industrial bleaches, food preservatives and pharmaceutical drugs are just a few more examples.Formic AcidFormic acid is responsible for the sting of some types of ants.Hexanoic AcidIt has the foul odor associated with dirty socks and locker rooms. It also contributes to the unpleasant odor of ginkgo seeds.Acrylic AcidAcrylic acid and its esters readily combine with themselves by reacting at their double bond, forming homopolymers or copolymers which are used in the manufacture of various plastics, coatings, adhesives, elastomers, as well as floor polishes, and paints.TESTS FOR CARBOXYLIC ACIDS1. Litmus Test:Carboxylic acids turn blue litmus red.2. Sodium Bicarbonate Test:To a small portion of the organic compound taken in a test tube, a pinch of solid sodium bicarbonate is added. Evolution of carbon dioxide with brisk effervescence shows the presence of carboxylic acid. Alcohols do not give this test.3. Ester Test:In this test, the compound to be tested is warmed with small quantity of ethyl alcohol and 2-3 drops of concentrated sulphuric acid. The formation of sweet smelling vapors indicates the presences of some carboxylic acid. The sweet smelling vapors are due to the formation of some ester by reaction between the acid and ethyl alcohol.4.Fluorescein Reaction: A little of the substance is heated with Conc.H2SO4 & Resorcinol in a dry test tube. It is cooled & then poured into a beaker containing excess of NaOH. A red solution with intense green fluorescence. Presence of dicarboxylic acid.5. Anhydride formation:A little of the acid is heated in a dry china dish covered with an inverted funnel whose stem is closed. It is then cooled. White shiny needles are deposited on the sides of the funnel. Presence of dicarboxylic acidREFERENCES

http://humantouchofchemistry.com/fruity-facts-about-carboxylic-acid.htmhttp://www.ck12.org/book/From-Vitamins-to-Baked-Goods%3A-Real-Applications-of-Organic-Chemistry/section/6.3/http://www.preservearticles.com/201101022309/uses-of-carboxylic-acids.htmlhttp://academics.wellesley.edu/Chemistry/chem211lab/Orgo_Lab_Manual/Appendix/ClassificationTests/carboxylic.htmlhttp://www.preservearticles.com/201101022310/tests-for-carboxylic-acids.htmlhttp://www.docbrown.info/page13/ChemicalTests/ChemicalTestsf.htm#KEYWORDS http://vlab.amrita.edu/?sub=2&brch=191&sim=345&cnt=1http://mchem.weebly.com/uploads/9/2/0/5/9205056/functional_group_tests.pdfhttp://www.britannica.com/science/carboxylic-acid/Reactions