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‘CHM136 > Term Test 1 Vocab > Flashcards

Term Test 1 Vocab Flashcards

1
Q

covalent bond

A

two electrons shared between 2 nuclei (localized covalent bond)

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2
Q

Trigonal Planar

A

flat molecule, has pi bond/sp2 orbitals, bond angle of 120°

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3
Q

Tetrahedral

A

pyramid shaped, sp3 hybridized, 4 substituents or 3 and a lone pair, bond angle is 109.5°

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4
Q

sp3 orbitals

A

3 p orbitals blended with 1 s, cannot form a pi bond as all p orbitals are already used in sigma bond

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5
Q

sigma bond

A

localized electrons, overlap of sp3 orbital and p orbital

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6
Q

Which orbital is involved in pi bond

A

p orbital excluded from sp2 hybridization will be involved in pi bonding

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7
Q

pi bond

A

delocalized, easily broken

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8
Q

linear molecule

A

sp orbitals, two pi bonds formed from the two p orbitals not involved in hybridization, bond angle of 180°

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9
Q

Is a double bond twice as strong as a single bond?

A

No, because pi bond is weaker than sigma bond and a double bond is composed of a pi and sigma bond.

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10
Q

Difference between polar and polarizable

A

Polar is when one atom in a molecule carries a negative charge more than the other one (ex. H - Cl, chlorine is more negative). Polarizable is the response of the bond to a dynamic system, electrons of larger molecules are further from nucleus and can be pulled away more easily.

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11
Q

The larger the atom…

A

…the more likely the bond can be polarized. A temporary dipole movement can be formed just by electron fluctuations around the atom.

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12
Q

Electronegativity increases and decreases in which way on periodic table?

A

Decreases as you go down a period, and increases as you go across the period.

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13
Q

Give examples of groups that donate electrons

A

Electron donating groups have low electronegativity and include: CH3, CH2CH3, Li, Mg, Al (metals)

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14
Q

dipole moment

A

measurable property that describes a separation of charge in the molecule, vector sum of all bond dipoles

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15
Q

Electron numbers of common elements

A 
1 - H, Li
4 - C
5 - N, P
6 - O, S
7 - Cl, Br, F
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16
Q

Formal charges

A

electron bookkeeping, sum of all formal charges must equal overall charge of the molecule.

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17
Q

formal charges can give you info about?

A

p orbitals

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18
Q

making bonds…

A

releases energy (this is why atoms bond because they are more stable bonded than separate)

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19
Q

breaking bonds…

A

absorbs energy

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20
Q

Aufban

A

lowest energy orbitals fill first. 1s, 2s, 2p, 3s, 3p, 4s, 3d

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21
Q

pauli exclusion

A

electrons have up spin and downspin only 2 e- can occupy an orbital and must have opposite spin

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22
Q

Hund’s rule

A

If two or more empty orbitals of equal energy are available, one electron occupies each with parallel spins until all orbitals are half full.

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23
Q

Why are sp3 bonds strong?

A

the orbitals are oriented strongly in a certain direction so it allows for better overlap of orbitals in a bond.

24
Q

Bond character of CH4 molecule

A

each C-H bond has strength of 439 kJ/mol and bond angle of 109.5°, length of 109 pm.

25
Q

Resonance Structures

A
  • do not change geometry of molecule in ANY WAY
  • forms only differ in their placement of pi bond electrons and lone pairs
  • one alone is wrong, molecule is blend of all of them, though some are upweighted
26
Q

Resonance Rules (in order of most importance)

A
  1. Number of pi bonds - delocalization of electrons stabilizes the molecule so form with most pi bonds makes greatest contribution to its stability (don’t move pi bonds from benzene ring, it will decrease stability)
  2. formal charges - fewer formal charges are more important. If forms have equal numbers of formal charges then the form that has the most EN atoms carrying neg charge and least EN atoms carrying pos charge is better
  3. Inductive effects - electron donating groups (alkyls) help to stabilize positive charge (give electrons to positive site), electron withdrawing groups (halogens, O, N) pull electrons and thus stabilize negative charge.
27
Q

Why is the terminal carbon on allene twisted? (C3H4)

A

middle carbon is sp hybridized, is bonding with two carbon substituents which are sp2 hybridized. The two empty orbitals on the middle carbon are not on the same plane and thus the pi bonds formed are at different angles.

28
Q

Similarities in structure imply…

A

similarities in properties and behaviour

29
Q

Amide

A

NH

30
Q

Amine

A

NH2

31
Q

carboxylic acid

A

Cooh (C double bonded to O, then other substit bonded to OH)

32
Q

Bronsted base

A

proton acceptor (hydrogen bonds to it)

33
Q

Bronsted acid

A

hydrogen donator (is deprotonated)

34
Q

Conjugate acids and bases

A

the resultant molecule when a site is protonated or deprotonated. Every acid has a conjugate base, and every base has a conjugate acid (base OH and conjugate acid H20)

35
Q

Lewis Base

A

electron pair donator (bonds with atom that has empty orbital)

36
Q

Lewis Acid

A

electron pair acceptor (has an empty orbital)

37
Q

Reaction always goes…

A

from stronger acid to weaker acid

38
Q

Water can act as

A

acid or base, pKa of 15

39
Q

The lower the pKA

A

The stronger the acid. A very high pKa indicates a basic species. Water is neutral. For something to be acidic look for lower than 15. For basic look for higher than 15.

40
Q

What does resonance tell us about acidity?

A

If the conjugate base of an acid can be resonance stabilized (by inductive effects or delocalization of electrons) it means the acid is more reactive than if it can’t be resonance stabilized. Resonance influences the ability of a base to share electrons (resonance stabilized bases are weak because the electrons that would bond to proton to form acid are delocalized). Weaker conjugate base=stronger acid

41
Q

Why is context important for acidity?

A

Acidity is always in context to the base you are reacting with. An OH functional group is acidic (in the same way water can act as an acid) but pay attention to carbon parent chain. Hydrocarbons effectively have 0% chance of donating H+ because C-H bonds are very strong so the longer the parent chain the weaker the acid.

42
Q

Most organic molecules and solvents are…

A

polar or weakly polar depending on length of parent chain (smaller organic molecules like acetone, ethanol, and ether are weakly polar)

43
Q

What can dissolve in water (interrupt the intermolec. forces between the water molecules)?

A

many ionic inorganic molecules (salts), small polar organic molecules,

44
Q

How to increase water solubility of an acid?

A

react with base to create charged species

45
Q

Alkanes

A

non-polar, LOW REACTIVITY

46
Q

Naming alkanes

A

2,3,4,5,6 - pentahydroxyhexanol (first part is location, second part is substituents, third part is parent chain)

47
Q

constitutional isomers

A

compounds with same molecular formula but a different connectivity of their atoms

48
Q

primary carbon

A

carbon bonded to only one other carbon

49
Q

secondary carbon

A

carbon bonded to two other carbons

50
Q

Saturated hydrocarbons are…

A

molecular scaffolds. LOW REACTIVITY. Regions that are saturated hydrocarbons are not reactive. On a huge alkyl molecule look for areas that could be reactive (acidic or basic)

51
Q

alkanes

A

C(n) H(2n+2)

52
Q

dihedral torsion angle

A

four atoms control this, 2 that make the axle, then other two can rotate about the bond

53
Q

torsional strain

A

strain from bonds eclipsing each other. drives molecules away from eclipsed formation.

54
Q

steric strain

A

strain that arises when atoms not bonded to one another are forced abnormally close (electron density in atoms repelling on another)

55
Q

anti conformation

A

180° dihedral angle, no torsional strain, need to have substituted molecule to have an anti conformation

56
Q

gauche conformation

A

60° angle between substits, no torsional strain, need to have substituted molecule to have an anti conformation

‘CHM136 (2 decks)

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