University:
The University Of Western Ontario
Course:
2223B | Organic Chemistry of Biological Molecules
Academic year:

2023
Views:

344

Pages:

2
Author:

Cole M

Alcohols & Phenols Alcohol Nomenclature: The primary/secondary/tertiary means how many carbons are also bonded to the carbon attached to the alcohol group Add stereochemistry to the beginning of the name If two alcohol groups, you can use trans/cis depending if they point in the same or opposite directions Properties of Alcohols: Introducing an alcohol to an alkane will increase the boiling point because of the introduction of hydrogen bonding capabilities As long as the number of carbon atoms is low and there is an alcohol group, it will be largely soluble in water (the more carbon atoms introduced to the alcohol, the least likely it is to be soluble) Alkoxide is the conjugate base to an alcohol Biological Oxidation of Ethanol: Your body takes care of alcohol (ethanol primarily) through the biological oxidation of alcohols The breakdown of alcohol occurs in the liver in two steps (shown on the right) Oxidation of Alcohols: 1° alcohols are oxidized to form aldehydes after one oxidation and then carboxylic acids after a second oxidation 2° alcohols are oxidized to ketones 3° alcohol cannot be oxidized because there is no alpha hydrogen PCC allows oxidation to stop at the aldehyde while Cr compounds will go all the way to carboxylic acid (for 2° alcohols it doesn’t matter, you can use both) Protection of Alcohols: Li+C2H- can be a great nucleophile, but also a great base, so that it won’t nucleophilically attack but instead take the proton from the hydroxyl group as shown on the right → Therefore, you need a protecting group in order to make sure it doesn’t attack the hydroxyl group The protecting group can be TBDMSCl, which will attach to the oxygen, kick off the H, and protect it from deprotonation, then you would do your regular reaction, and finish it off with TBAF in order to take back the TBDSM off the oxygen and replace it with a proton in acid (regenerating the hydroxyl group) Preparation of Mesylates & Tosylates: Some reasons to form tosylates is to have a better nucleophilic substitution reaction (OTs is an amazing leaving group, much better than OH) so that a halogen or such can come in and kick it off relatively easily → keeps stereochemistry A mesylate is important as well because it is another excellent leaving group (OMs) SN1 & SN2 Reactions of Alcohols: 1° and 2° alcohols react with nucleophiles via SN2 and has an inversion of stereochemistry SN2 is concerted, meaning that the bond breakage/forming occurs at the same time 3° alcohols react with nucleophiles via SN1 SN1 means that the bonds breaks first (stabilized because it is 3°) and then the new bone forms (racemization of stereochemistry because the carbocation intermediate is sp2 hybridized, meaning that the nucleophile can attack from either side) Aromatic Stability of Benzene: Bromine adds across a double bond in cyclohexane leading to different stereoisomers, but you cannot do this for benzene (it is super stable due to aromaticity) A compound is aromatic if: 1. Contains a ring of continuously overlapping p orbitals (planar) 2. Has 4n + 2 (Huckel’s rules) pi electrons in the ring Aromatic Heterocycles: A heterocycle is a molecule that has a different atom other than carbon within the ring If electrons are in sigma orbitals, they do not participate in resonance, but those in pi orbitals can participate in resonance