Organic Chemistry- Chapter 4

Acids & Bases

Acidity increases as you move…

To the right and down the periodic table

What forms when an acid donates a proton?

a conjugate base

What forms when a base accepts a proton?

a conjugate acid

True or False:

Strong acids do not give up their proton easily.

False

True or False:

The weaker acid and weaker base pair is favored at equilibrium.

True

Define the term:

Bronsted acid

proton donor

Define the term:

Bronsted base

proton acceptor

As pKa decreases…

acidity increases

True or False:

The lower pKa value is favored at equilibrium

False

Conjugate acids of strong bases are…

weak

Conjugate bases of weak acids are…

strong

True or False:

The more electronegative an atom is, the more acidic the H attached to it will be

True

The pull of electron density through sigma bonds caused by electronegativity differences of atoms

Inductive Effect

True of False:

The more electronegative the atom and the closer it is to the site of the negative charge, the smaller the effect on acidity.

False

Delocalization is a ___________ effect.

Stabilization

The more stable the molecule, the more ______ the molecule.

Acidic

The more “s” character a molecule has, the _____ acidic that molecule is.

More

Why are molecules with more “s” character more acidic?

S orbitals are the closest orbital to the nucleus, so the electrons are closer to a positive charge, making the molecule more stable.

List the 4 factors determining acidity strength in order of importance.

Element Effect

Inductive Effect

Resonance Effect

Hybridization Effect

pKa value of a carboxylic acid

5

pKa value of a thiol

7

pKa value of a protonated amine

10

pKa value of an alcohol

15

pKa value of water

15.7

pKa value of a ketone

20

pKa value of an alkyne

25

pKa value of an amine

38

pKa value of an alkene

45

pKa value of an alkane

50

The acidity of a compound is mostly governed by the functional group on which the ____________ is found.

acidic proton

Strong bases typically have a pKa value of…

>12

Are amines acidic or basic?

Basic

Strong bases typically have a net ________ charge.

Negative

True or False:

In order for a molecule to be a base, it’s lone pair can not be used up in resonance

True

Define the term:

Lewis Acid

Electron pair acceptor; electrophile

Define the term:

Lewis Base

Electron pair donor; nucleophile

True or False:

Elements with unfilled valence shells can act as Lewis bases.

False

Any species that is electron deficient and is capable of accepting an electron pair

Lewis acid

True or False:

All Lewis Acids are Bronsted-Lowry Acids, but the reverse is not necessarily true.

False

Define the term:

Electrophile

Electron poor site

Define the term:

Nucleuphile

Electron rich site

When drawing arrows to describe what happens in a chemical reaction, the arrow indicates the movement of…

Electrons

Electron source

Electron sink

An area with relatively low electron density

Protonation

Adding a proton

Deprotonation

Taking a proton away

True or False:

Weak acids/bases completely ionize in water.

False

What is the sign (+/-) of the pKa value if the majority of acidic molecules are dissociated in water?

-

What is the sign (+/-) of the pKa value if the majority of acidic molecules remain undissociated in water?

+

True or False:

An acid will usually be deprotonated if its pKa is two or more units lower than the pH of an aqueous solution

True