Formation of cyanohydrins Formaldehyde > aldehyes > ketones

Natural Occurring Cyanohydrins mandelonitrile - insects and plants use for defense against predators

Vitamin B-17 - Laetrile Amygdalin - The seeds of apples, apricots, cherries, peaches, plums, nectarines. “cures cancer by entering cancer cells which has the Enzyne which releases the HCN which kills cell!!!”

Formation of Imines - Condensation of Carbonyl Compd with Primary Amines carbinolamine imine or Schiff Base

OLD FASHION MECHANISM LASSO OUT HOH Lasso out a molecule of HOH and connect the two resulting residues - condensation

Modern Day Mechanism First step Typical base-mediated nucleophilic addition Surely you must be tired to seeing this mechanism

Second Step - acid catalyzed dehydration

Importance of pH in Schiff Base Formation (IMINES) 1)Must be acidic since dehydration is acid catalyzed 2) Can not be too acidic or primary amine will Be protonated (i.e. lone pair electrons tied up) pH 4.5 is best

Examples

SCHIFF BASES IN BIOCHEM GLYCATION - linked to diabetic complications

Interaction of cis-retinal with lysine side chain +

Give structures of C=O and RNH2 to prepare imines REVERSE OF CONDENSATION WHICH IS DEHYDRATION!!

Addition of Hydroxylamine and Phenylhydrazines

Addition of Alcohols-Formation of Acetals NOTE: carbon is attached to two oxygens unlike diols, acetals are quite stable in basic and neutral conditions HOWEVER - not stable in acid /HOH reverts back to free carbonyl compound

HEMIACETAL Benzaldehyde dimethyl ketal

Mechanism of Acetal Formation Acid catalyzed addition of ROH to Carbonyl Lose of Water Addition of alcohol HOTs