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Psych/Soc > OChem Class 1 > Flashcards

OChem Class 1 Flashcards

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1
Q

Saturated Alkanes

A

All carbons have maximum number of H atoms attached

CnH2n+2

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2
Q

Degree of Unsaturation

A

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

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3
Q

Properties of Unstable vs Stable molecule

A

Unstable:

  • high reactivity with environment
  • shorter lifespan
  • high in energy

Stable:

  • Low reactivity with environment
  • longer lifespan
  • low in energy
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4
Q

Ring strain & strain energy

A

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
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5
Q

What does ring strain do?

A

Destabilizes ring, weakens C-C bond, increases reactivity

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6
Q

What molecule can relieve ring strain?

A

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

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7
Q

Electropositive vs Electronegative substituents

A

Electropositive - Donate e- density (eg. alkyl groups)

Electronegative - Withdraw e- density (eg. O, halogens)

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8
Q

Induction

A

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

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9
Q

Carbocation stability

A

tertiary > secondary > primary > methyl

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10
Q

Carboanion stability

A

tertiary < secondary < primary < methyl

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11
Q

Resonance stabilization

A

Occurs due to delocalization of electrons

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

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12
Q

Resonance rules

A
  1. Octet satisfied for ALL atoms
  2. Least formal charge
  3. Negative charge on the more electronegative atom
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13
Q

Bronsted-Lowry Acid

A

Donates H+ and leaves behind conjugate base

The more stable conjugate base is, the strong the acid

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14
Q

3 factors that influence conjugate base stability

A
  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
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15
Q

Strong acids to weak acids list

A

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

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16
Q

Nucleophile vs Electrophile

A

Electrophile is electron loving, accepts e- pair

Nucleophile is nucleus loving, donates e- pair

17
Q

Lewis base vs acid

A

Lewis base donates e-

Lewis acid accepts e-

18
Q

Nucleophilicity trend

A

Increases right to left, top to bottom

19
Q

Leaving Groups

A
  • 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
Q

What makes a molecule more stable?

A

Resonance
Induction
Size
Electronegativity

21
Q

What does reactivity depend on?

A

Leaving group ability
Nucleophile strength
Acid strength

22
Q

Isomer

A

Same molecular formula with different compounds

23
Q

Constitutional vs Conformational Isomer

A

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

Conformational
- same atomic connectivity & identical chemical & physical properties

24
Q

Newman projections for n-butane

A

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
Q

When drawing chair conformations

A
  • 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
Q

Trans vs cis

A

Trans - both groups facing opposite direction

Cis - both groups facing same direction

27
Q

Chirality

A

Not superimposable on its mirror image

No plane of symmetry

28
Q

How to locate a chiral center

A
  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
Q

How to calculate number of isomers knowing how many chiral centers

A

2^n

n = # of chiral centers

30
Q

Optical Acitivty

A

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

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

31
Q

Assigning priority to atoms bonded to chiral center

A
  1. Atom with highest atomic number has highest priority
  2. Heavier isotopes have higher priority
  3. if two atoms on a chiral center are identical, move to the next atom to find the first point of difference; the atom with the highest atomic number takes priority
  4. Bonded atoms count as an equivalent number of single bonded atoms
32
Q

Absolute configuration (R & S)

A
  1. Assign priority (1-4) to atoms directly bonded to chiral center
  2. Ensure lowest priorty substituent is in the “away” (dashed) position. If not, switch it with the substituent that is taking that place
  3. Trace arc going from 1-3
    - Counter-clockwise = S
    - Clockwise = R
    * If an exchange happened in step 2, use the reverse letter
33
Q

Steroisomers

A

Same connectivity but differ in spatial arrangement

Can be diasteromer, enantiomer or meso compound

34
Q

Enantiomer

A
  • Non superimposable, mirror images
  • Opposite configuration at ALL chiral centers
  • Each enantiomer has optical rotation of equal magnitude, but opposite sign
  • All other chemical & physical properties are identical
  • Process to separate enantiomers is resolution
35
Q

Meso Compounds

A
  • Must contain chiral centers
  • Have internal plane of symmetry
  • not optically active (achiral)
36
Q

Diastereomer

A
  • Non-superimposable, non mirror image
  • All chemical & physical properties are different
  • Unrelated optical activities
  • Opposite configuration for at least ONE but not all chiral centers

Can be either Geometric isomer OR Epimer

37
Q

Geometric Isomer

A

Does not need chiral center
Restricted rotation about double bond or ring
All chemical/physical properties are different

Z/E —> Cis/trans
Trans is better because less steric interaction

38
Q

Epimers

A

Differ at ONLY ONE chiral center

Psych/Soc (24 decks)

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