Chem. 17 - Chpt. 5 Reading Notes

Front 1

What is the electron donor called?

Back 1

Nucleophile

Front 2

What is the electron acceptor called?

Back 2

The electrophile

Front 3

Is a nucleophile an anion or a cation?

Back 3

Anion, (negatively charged, so wants to give off the excess electrons)

Front 4

Is an electrophile an anion or a cation?

Back 4

Cation, (positively charged, so wants the negative charge to neutralize it)

Front 5

Are full orbitals higher or lower in energy than empty orbitals?

Back 5

Full orbitals are lower in energy than empty orbitals, (which is why they want to be filled)

Front 6

Why is activation energy required in the transfer of electrons to orbitals?

Back 6

When the electrons move into an empty orbital, they have to go up in energy and this is part of the activation energy

Front 7

When atomic orbitals interact, how many new molecular orbitals are formed?

Back 7

Two - one above and one below the old orbitals

Front 8

When is the energy gain of interacting orbitals the greatest and when is it the least?

Back 8

Greatest when the 2 orbitals are the same and least when the 2 orbitals are very far apart.

Front 9

What are the relevant orbitals of the nucleophile called?

Back 9

Highest occupied molecular orbitals, (HOMO), because electrons want to come from the highest state of energy

Front 10

What are the relevant orbitals of the nucleophile called?

Back 10

Lowest unoccupied molecular orbital, because electrons want to go to the lowest state of energy

Front 11

Why do molecules attract each other?

Back 11

1. Attraction of opposite charges
2. Overlap of high-energy filled orbitals with low-energy empty orbitals

Front 12

How must molecules approach one another in order to react?

Back 12

1. Enough energy to overcome the repulsion
2. The right orientation to use any attraction

Front 13

What characteristic do the most common type of nucleophiles have?

Back 13

A nonbonding lone pair of electrons, (usually on heteroatoms, such as O,N,S, or P).

Front 14

Give an analogy to think of nucleophiles and electrophiles.

Back 14

Nucleophiles are involved in real estate that costs a lot, such as "loan" pairs, (which is why they are in the negative)

Electrophiles are empty real estate, (empty orbitals), that cost less money, so the electrons want to move there.

Front 15

When there are no lone pair electrons to supply high-energy nonbonding orbitals to donate electrons, what is the next best provider?

Back 15

Lower-energy filled pie orbitals rather than the even lower-energy sigma bonds. For example, simple alkenes are weakly nucleophilie and react with strong electrophiles, such as bromine.

Front 16

What is an acid in terms of electrophiles/nucleophiles?

Back 16

Electrophiles
- Protic acids can donate protons to nucleophiles
- Lewis acids can donate more complicated cations to nucleophiles

Front 17

What part of a C=O bond does a nucleophile attack?

Back 17

The "crotch" of the double bond

Front 18

Where can nucleophiles donate electrons to and where can electrophiles put the electrons?

Back 18

Nucleophiles may donate electrons from:
1. a lone pair
2. a pie bond
3. a sigma bond

Electrophiles may place electrons in:
1. an empty orbital
2. an anti-bonding orbital of a pie bond or even a sigma bond

Front 19

What are some nucleophilic functional groups?

Back 19

NH2 and OH, because they have nonbonding loan pairs

Front 20

What are some electrophilic functional groups?

Back 20

Carbonyl compounds and alkyl halides, because they have low-energy LUMOS, (pie bond for C=O and sigma bond for C-X, respectively)

Front 21

If the starting materials had no overall charge, can the products?

Back 21

No, so if we start with a neutral molecule and make a cation, we must make an anion too.

Front 22

When a nucleophile arrow goes to the crotch of a carbonyl group, where does the subsequent arrow of the carbonyl group go?

Back 22

It goes from the middle of the double bond to the top of the O

Front 23

What is the leaving group?

Back 23

Functional group on the electrophile that makes off with the electrons of the old sigma bond

Front 24

What is heterolytic fission/heterolysis?

Back 24

Leaving group takes both electrons from the old pie bond

Front 25

What is homolytic fission?

Back 25

When a sigma bond breaks on nucleophile, rather than moving to one of the atoms as in heterolysis, one electron can go in either direction. Both fragments have an unpaired electron and are known as radicals.

Front 26

How is homolytic fission represented?

Back 26

Fish hooks

Front 27

What can push a mechanism?

Back 27

A lone pair or an anion

Front 28

What can pull a mechanism?

Back 28

A cation, an empty orbital, or the breaking of a reactive weak pie bond or sigma bond

Front 29

What are 3 guidelines for writing your own arrow-pushing mechanisms?

Back 29

1. Decided whether to think in a push or pull manner
2. Mark lone pairs on the nucleophilic atom
3. Curly arrows always move in the same direction. They never meet head on.