Organic Chemistry

Unit X Organic Chemistry Shelly Wei Mathew Jiang Johnny Yu Mike Chi

A prior question: What is ORGANIC CHEMISTRY? Organic Chemistry: It is a chemistry sub-discipline involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e. matter in its various forms that contain… Carbon Atoms!

*Review Questions* What is functional groups? • Functional Groups: A Functional group is a specific group of atoms which exists in a molecule and gives a molecule an ability to react in a specific manner or gives it specific properties.  Different groups of atoms have different manner or properties.

Any Examples of functional groups? • Halides • Carbon-carbon double bonds (in alkenes) • Carbon-carbon triple bonds (in alkynes) • Alcohol • Aldehydes • Ketones • ….

Now… • There is something that can also be categorized into functional groups, and it is called… Ether!

Organic Chemistry LessonCarboxylic Acids Mathew Jiang Mike Chi

What kind of substance would you judge only after your smelling? • Yes, it is… Vinegar!

What is carboxylic acid? “Organic Acids” • Carboxylic Acid: It is an organic compound which contains a COOH group. The COOH group is also sometimes shown as… What is R? R is a monovalent functional group. Something that possesses a charge of -1.

Pop Quiz~ Carbonyl: A carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. What is carbonyl? What is hydroxyl? Hydroxyl: A hydroxyl is a chemical functional group containing an oxygen atom connected by a covalent bond to a hydrogen atom, a pairing that can be simply understood as a substructure of the water molecule. R-OH H O Carboxylic Acid!!!

How to name it? • Let me show you some examples… • CH3COOH • HCOOH • CH3-CH2-CH2-COOH • Ethanoic acid • Methanoic acid • Butanoic acid Why? Find the regulation?

How many carbons are there in carboxylic acid? • The number of carbons  Prefixes • Prefix + oic + Acid •  That is how the name comes from!

Physical Properties Solubility Carboxylic acids are polar. Because they are both hydrogen-bond acceptors (the carbonyl) and hydrogen-bond donors (the hydroxyl), they also participate in hydrogen bonding. Carboxylic acids usually exist as dimeric pairs in nonpolar media due to their tendency to “self-associate.” Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas higher carboxylic acids are less soluble due to the increasing hydrophobic nature of the alkyl chain. These longer chain acids tend to be rather soluble in less-polar solvents such as ethers and alcohols.

Boiling points • Carboxylic acids tend to have higher boiling pointsthan water, not only because of their increased surface area, but because of their tendency to form stabilizeddimers. • Carboxylic acids tend to evaporate or boil as these dimers. For boiling to occur, either the dimer bonds must be broken, or the entire dimer arrangement must be vaporized, both of which increase enthalpy of vaporization requirements significantly. *A dimeris a chemical entity consisting of two structurally similar monomers joined by bonds that can be either strong or weak, covalent or intermolecular.

Acidity Carboxylic acids are typically weak acids, meaning that they only partially dissociate into H+cations and RCOO– anions in neutral aqueous solution. For example, at room temperature, only 0.4% of all acetic acid molecules are dissociated. *Electronegative substituents give stronger acids.

Odor • Carboxylic acids often have strong odors, especially the volatile derivatives. Most common are acetic acid (vinegar) and butanoic acid (rancid butter). On the other hand, esters of carboxylic acids tend to have pleasant odors and many are used in perfumes. It must be vinegar… because of its odor.

Practice Problems • Pg.240 #37  Just identify which are the carboxylic acids?

Thanks for your attention!

Organic Chemistry