Ochem Class 1

Question 1

Resonance Rules

Answer 1

1. The octet rule satisfied for all atoms
2. The least formal charge
3. Negative charge located on most negative atom

Question 2

Minor versus Major resonance

Answer 2

Major most hybridization (most stable)
Minor least stable (most charged)

(filling the octet rule takes priority of the number of charges present)

Question 3

Brønsted-Lowry- Acids donate or accept protons?

Answer 3

Acids donate protons ( H+) and leave behind a conjugate base

Question 4

Nucleophiles

Answer 4

Lewis base that donates a pair of electrons and creates a covalent bond
Increases with size of atom

Question 5

Electrophiles

Answer 5

Lewis acid that accepts a pair of electrons and acquires a covalent bond

Question 6

Leaving Groups

Answer 6

Good LG - resonance stabilization, weak base,
Bad LG - strong bases,
Acid catalysts can make bad LG into GL via protonation

Question 7

RISE Factors that influence stability

Answer 7

Resonance
Induction
Size
Electronegativity

Question 8

Optical activity

Answer 8

Can not be determined by looking at molecule. Has to use a palimater

Question 9

Chiral Centers R &S

Answer 9

1. Atom with highest atomic number
2. Heavier isotopes have higher priority
   Priority goes to the group attached with the highest atomic number.
3. Line dashed notation is opposite of only line notation

Question 10

Rearrange S and R

Answer 10

Lowest priority dashed line (away)
Clock wise is R
Counter clock wise is S

Question 11

Constitutional Isomers

Answer 11

Different atomic connectivity with same molecular formula

Question 12

Conformational Isomers

Answer 12

Rotation around a sigma bond. Same molecular formula and same connectivity
Staggered conformation (opposite R groups)
Eclipsed confirmation (overlapping R groups)
Gauche confirmation (not quite eclipsed)

Question 13

Stereoisomers isomers

Answer 13

Different special arrangements of atoms or substitutents

Question 14

Epimers

Answer 14

Differ at one chiral carbon

Question 15

Meso Compound

Answer 15

Has an internal pane of symmetry. Are superimposed that contains a chiral center. They are not optically active meaning they are achiral. The absolute configuration of a meso compound is R,S.

Question 16

Inductive Effects

Answer 16

The effect on electron density in one portion of a molecule due to electron-withdrawing or electron-donating groups elsewhere in the molecule

Question 17

Effects of substituents on acidity

Answer 17

Halogens are electron withdrawing groups that can increase the acidity of an acid molecule

Question 18

Nucleophilicity

Answer 18

Increases as negative charge increases
Increases going down the periodic table
Increases going left on the periodic table

Question 19

Staggered

Answer 19

Anti conformation

Question 20

Eclipsed

Answer 20

Sun conformation

Question 21

Gauche conformation

Answer 21

The largest groups on the central carbons are 60 degrees apart

Question 22

Stereoisomerism

Answer 22

Same formulae and connectivity but differ in spatial arrangement. Not superimposable

Question 23

Diastereomers

Answer 23

These are enantiomers with more than one chiral center. S does not superimpose with R

Question 24

Epimers

Answer 24

Subclass of diastereomers that differ in their absolute configuration at a single chiral center . E.g. d galactose, d glucose, and d allose

Question 25

Anomers

Answer 25

Epimers that close as a result of ring closure

Question 26

Geometric Isomers

Answer 26

Differ in orientation around a ring. Substituents could be on opposite of the same side of the ring. Cis - same side Trans - different sides

Question 27

Z or E Notation

Answer 27

Highest priority groups on same side is Z Highest priority groups on different side E

Question 28

Carbocations

Answer 28

Carbocations are positively charged ions that are localized on carbon Tertiary are more stable, less reactive, and lower energy continue to methyl which is less stable, more reactive and higher energy

Question 29

Carboanions

Answer 29

Negatively charged species with a full negative charge localized on carbon. Methyl is more stable, less reactive, and lower energy going toward tertiary less stable, more reactive, and higher energy

Question 30

Elute

Answer 30

extracting one material from another by washing it with a solvent

Question 31

H’ NMR Peaks Represent

Answer 31

Number of chemically different hydrogens

Question 32

Heat of Combustion

Answer 32

Heat of combustion is equal to the proportional energy of a molecule