Organic Chemistry Chapter 4: Analyzing Organic Reactions Flashcards
(55 cards)
What is a lewis acid?
electron acceptors
What is a lewis base?
electron donor
What is a B-L acid?
proton donor
What is a B-L base?
proton acceptor
What are amphoteric molecules?
can act as either acids or based, depending on reaction conditions. ex. water
What is the acid dissociation constant?
Ka - a measure of acidity, the equilibrium constant corresponding to the dissociation of an acid into HA into a proton and its conjugate base
What is pKa?
the negative logarithm of Ka — the lower the pKa, the stronger the acid
What is the pKa trend in the periodic table?
decreases down the periodic table and increases with electronegativity
What are alpha hydrogens?
hydrogens connected to an alpha carbon (carbon adjacent to a carbonyl
What are common acidic functional groups?
alcohols, aldehydes, ketones, carboxylic acids and c.a. derivatives
What are common basic functional groups?
Amines and amides
What are nucleophiles?
nucleus loving and contain lone pairs or pi bonds. They have increased electron density and often carry a necative charge.
What can affect nucleophility?
charge, electronegativity, steric hinderance and the solvent
What are common nucleophiles?
amino groups
What are electrophiles?
electron-loving and contain a positive charge or are positively polarized.
What are common electrophiles?
alcohols, aldehydes, ketones, carboxylic acids & derivatives
What are leaving groups?
molecular fragments that retain the electrons after heterolysis. good leaving groups can stabilize additional charge through resonance or induction. Weak bases make good leaving groups.
What is heterolysis?
opposite of coordinate covalent bond formation - a bond is broken and both electrons are given to one of the two products.
What types are almost never leaving groups?
Alkanes and hydrogen ions because they form reactive anions
What are the steps of a unimolecular nucleophilic substitution?
- leaving group leaves, forming a carbocation, an ion with a positively charged carbon atom.
- the nucleophile attacks the planar carbocation from either side, leading to a racemic mixture of products
What do Sn1 reactions prefer?
more substituted carbons because the alkyl groups can donate electron density and stabilize the positive charge of the carbocation.
What is the rate of an Sn1 reaction dependent on?
only on the concentration of the substrate
What is a bimolecular Sn2 nucleophilic substitution?
Happens in one step - nucleophile attacks at the same time as the leaving group leaves.
What happens to the stereochemistry in an Sn2 reaction?
Nucleophile performs a backside attack, which leads to an inversion of stereochemistry.
