Test 2 Study

Question 1

All reactions involve the breaking of bonds and formation of bonds therefore most organic reactions are between a _____ and an _____.

Answer 1

nucleophile; electrophile

Question 2

_____ are an electron-deficient species… meaning they can ___ a pair of electrons.

Answer 2

electrophiles; accept

Question 3

Where can electrophiles accept new electrons from? What new bond do they form?

Answer 3

Electrophiles can accept new electrons from nucleophiles to form covalent bonds.

Question 4

What mechanism shows movement of electrons from the nucleophile to electrophile?

Answer 4

The reaction mechanism

Question 5

Explain what reaction mechanism happens between a negatively charged Br atom and a positively charged C atom.

Answer 5

The negatively charged Br atom will form a covalent bond with the positively charged C atom.

Question 6

Brønston-Lowry acids are proton-____ and bases are proton-_____.

Answer 6

donors; acceptors

Question 7

What conjugate acids and bases could these reactants yield?
HCl (acid) + H2O (base) –> ?

Answer 7

Cl- (conjugate base) + H3O+ (conjugate acid)

Question 8

What conjugate acids and bases could these reactants yield?
NH3 (base) + H2) (acid) –> ?

Answer 8

NH4+ (conjugate base) + OH- (conjugate acid)

Question 9

What can the pKa value tell you about the strength of an acid?

Answer 9

The lower the pKa, the stronger the acid.

Question 10

At equilibrium, the pKa of reactants and products will be what?

Answer 10

of equal value

Question 11

Explain a unidirectional acid/base reaction.

Answer 11

The MUCH stronger acid will yield a MUCH weaker base. The products and reactants have highly different pKa’s.

Question 12

The more electronegative an atom is, the more _____ the conjugate base.

Answer 12

stable

Question 13

Rank the following in order of decreasing pKa:
CH4, H2O, HF, NH3

• remember that the lower the pKa, the more unstable the acid *

Answer 13

HF (F-) > H2O (HO-) > NH3 (NH2-) > CH4 (CH3-)

Question 14

What is spreading electron density over a larger area called?

Answer 14

polarizability

Question 15

The bigger the atom, the more ____ the conjugate base.

Answer 15

stable

Question 16

Rank the following acids in the order of increasing pKa:
HF, HCl, HBr, HI

• remember that the lower the pKa, the more unstable the acid *

Answer 16

HI (I-) < HBr (Br-) < HCl (Cl-) < HF (F-)

Question 17

Which is more acidic?:
propane-NH2 or propane-OH

Answer 17

propane-OH
Since N and O are in the same period, we will determine the acidity based on electronegativity. O is more electronegative than N on the periodic table.

Question 18

Which is more acidic?:
propane-SH or propane-OH

Answer 18

propane-SH
Since S and O are in the same group, we will determine the acidity based on size (polarizability). S is larger than O on the periodic table.

Question 19

Rank the following orbitals in order of increasing electronegativity:
sp2, sp3, sp

Answer 19

sp3, sp2, sp

Question 20

Rank the following acids from strongest acid to weakest acid:
C2H6, C2H4, C2H2

Answer 20

1) C2H2
2) C2H4
3) C2H6
Since C2H2 has a triple bond, then one carbon atom will have an sp orbital causing it to be a strong acid. C2H6 has a carbon with an sp3 orbital causing it to be a weak acid.

Question 21

What will happen to a weak acid if a hydrogen atom is removed?

Answer 21

The weak acid will yield a strong conjugate base.

Question 22

What is pulling electron cloud via sigma bonds?

Answer 22

Inductive effects