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Flashcards in OChem Class 1 Deck (38)
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1

Saturated Alkanes

All carbons have maximum number of H atoms attached

CnH2n+2

2

Degree of Unsaturation

H2 molecule is removed

DOU = (2n+2) - x /2

x = # of hydrogen atoms
n = # of carbon atoms

Halogen acts like hydrogen atoms
O2 does nothing
Nitrogen has to be subtracted from the total of hydrogen atoms

3

Properties of Unstable vs Stable molecule

Unstable:
- high reactivity with environment
- shorter lifespan
- high in energy

Stable:
- Low reactivity with environment
- longer lifespan
- low in energy

4

Ring strain & strain energy

Ideal sp3 bond angle is 109.5, if it differs from this, it'll cause ring strain

3 membered ring has more strain than 4
5 membered ring has minimal
6 =0
7 + = acts similar to 5 membered ring
14 = 0

5

What does ring strain do?

Destabilizes ring, weakens C-C bond, increases reactivity

6

What molecule can relieve ring strain?

H2 as a catalyst (usually in alkenes & alkyenes, not alkanes)

7

Electropositive vs Electronegative substituents

Electropositive - Donate e- density (eg. alkyl groups)
Electronegative - Withdraw e- density (eg. O, halogens)

8

Induction

Electrons in a sigma bond shift toward the more electronegative atom
FONClBrSCH

9

Carbocation stability

tertiary > secondary > primary > methyl

10

Carboanion stability

tertiary < secondary < primary < methyl

11

Resonance stabilization

Occurs due to delocalization of electrons

Electrons travel from nucleophillic (high negative charge) to electrophillic (low negative charge)

12

Resonance rules

1. Octet satisfied for ALL atoms
2. Least formal charge
3. Negative charge on the more electronegative atom

13

Bronsted-Lowry Acid

Donates H+ and leaves behind conjugate base
The more stable conjugate base is, the strong the acid

14

3 factors that influence conjugate base stability

1. Electronegativity- A more EN atom attached to H can handle negative charge better
2. Resonance - Increases stability of anionic conjugate base
3. Induction - proximity & electronegativity of EWG

15

Strong acids to weak acids list

HBr, HI, HCl, HNO3, H2SO4, HClO4 > Sulfonic acid > carboxylic acid > phenol > alcohol & water > ketone & aldehyde > sp hybrid > sp2 hybrid > sp3 hybrid

16

Nucleophile vs Electrophile

Electrophile is electron loving, accepts e- pair
Nucleophile is nucleus loving, donates e- pair

17

Lewis base vs acid

Lewis base donates e-
Lewis acid accepts e-

18

Nucleophilicity trend

Increases right to left, top to bottom

19

Leaving Groups

- Parallel acidity (good leaving group = good acid)
- A good LG means it is a weak base of a strong acid, resonance stabilized or neutral LG. (water)

20

What makes a molecule more stable?

Resonance
Induction
Size
Electronegativity

21

What does reactivity depend on?

Leaving group ability
Nucleophile strength
Acid strength

22

Isomer

Same molecular formula with different compounds

23

Constitutional vs Conformational Isomer

Constitutional (structural)
- different atomic connectivity thus different chemical & physical properties

Conformational
- same atomic connectivity & identical chemical & physical properties

24

Newman projections for n-butane

If methyl groups are 180° apart it is ANTI, and if H groups are 60° apart it is staggered (most stable)

If methyl groups are 60° apart it's GAUCHE (intermediate stable)

If methyl groups are 0° apart (eclipsed) it is SYN (least stable)

25

When drawing chair conformations

- Axial alternates up and down
- Equitorial alternates opposite to that
- When you have large substituent, better to be equitorial than axial because of unfavourable steric interactions

26

Trans vs cis

Trans - both groups facing opposite direction
Cis - both groups facing same direction

27

Chirality

Not superimposable on its mirror image
No plane of symmetry

28

How to locate a chiral center

1. sp3 hybridization
2. tetrahedral geometry
3. 4 different substituents

* carbons part of pi bond (double bond) won't have chiral center because it'll only have 3 groups NOT 4

29

How to calculate number of isomers knowing how many chiral centers

2^n
n = # of chiral centers

30

Optical Acitivty

Chiral molecules rotate plane-polarized light & are optically active
d = dextrorotary (clockwise) +
l = levorotary (counterclockwise) -

+/- --> optical rotation
d/l --> relative sterochemistry