University:
Eastern Kentucky University
Course:
CHE 361 | Organic Chemistry I
Academic year:

2020
Views:

284

Pages:

1
Author:

Kristopher Elliott

Organic Chemistry 4: Analyzing Organic Reaction Acids and Bases Lewis Acid:e- REDOX Reactions acceptor. Has vacant orbitals or + polarized atoms. Lewis Base: e- donor. Has a lone pair of e-, are often anions. Brønsted-Lowry Acid: Proton donor Oxidation: Raises oxidation state. Assisted by oxidizing agents. Oxidizing Agent: Accepts electrons and is reduced in the process. Brønsted-Lowry Base: Proton acceptor Amphoteric Can act as either acids or bases, depending on Molecules: reaction conditions. Ka: Acid dissociation constant. A measure of acidity. It is the equilibrium constant corresponding to the dissociation of an acid, HA, into a proton and its conjugate base. pKa: An indicator of acid strength. pKa decreases down the periodic table and increases with EN. p𝐾# =% −log%(𝐾# ) a -carbon: A carbon adjacent to a carbonyl. a -hydrogen: Hydrogen connected to an a -carbon. SN 1 Oxidation Number: The charge an atom would have if all its bonds were completely ionic. Reduction: Lowers oxidation state. Assisted by reducing agents. Reducing Agent: Donates electrons and is oxidized in the process. Chemoselectivity Both nucleophile-electrophile and REDOX reactions tend to act at the highest-priority (most oxidized) functional group. One can make use of steric hindrance properties to selectively target functional groups that might not primarily react, or to protect functional groups. SN 2 E1 E2 Solvents Nucleophiles, Electrophiles and Leaving Groups Nucleophiles: “Nucleus-loving”. Contain lone pairs or p bonds. They have #EN and often carry a NEG charge. Amino groups are common organic nucleophiles. Nucleophilicity: A kinetic property. The nucleophile’s strength. Factors that affect nucleophilicity include charge, EN, steric hindrance, and the solvent. Polar Protic Polar Aprotic Polar Protic solvents Acetic Acid, H2O, ROH, NH3 Polar Aprotic solvents DMF, DMSO, Acetone, Ethyl Acetate Electrophiles: “Electron-loving”. Contain a + charge or are positively polarized. More positive compounds are more electrophilic. Leaving Group: Molecular fragments that retain the electrons after heterolysis. The best LG can stabilize additional charge through resonance or induction. Weak bases make good LG. SN1 Reactions: Unimolecular nucleophilic substitution. 2 steps. In the 1st step, the LG leaves, forming a carbocation. In the 2nd step, the nucleophile attacks the planar carbocation from either side, leading to a racemic mixture of products. Rate=𝑘%[substrate] SN2 Reactions: Bimolecular nucleophilic substitution. 1 concerted step. The nucleophile attacks at the same time as the LG leaves. The nucleophile must perform a backside attack, which leads to inversion of stereochemistry. (R) and (S) is also changed if the nucleophile and LG have the same priority level. SN2 prefers less-substituted carbons because steric hindrance inhibits the nucleophile from accessing the electrophilic substrate carbon. Rate=𝑘%[nucleophile]%[substrate] Substrate Polar Protic Polar Aprotic Strong Small Strong Bulky Solvent Solvent Base Base SN 2 SN 2 SN 2 SN 2 SN 2 SN 2 SN 2 E2 SN1 / E1 SN 2 E2 E2 SN1 / E1 SN1 / E1 E2 E2 Methyl Primary Secondary Tertiary