chm136 test 1

Question 1

rules for comparing resonance forms

Answer 1

1. full octet
2. less formal charges
3. neg charge on more EN atoms, pos charges on more electropositive atoms
4. same charges far away, opp. charges close

Question 2

delocalized pi bond is…

Answer 2

when 2 electrons are shared among 2+ atoms

Question 3

what is necessary for resonance?

Answer 3

pi bonds or lone pairs

Question 4

resonance atoms are always ___ hybridized

Answer 4

sp2

Question 5

valence electrons are…

Answer 5

electrons in an orbital in an unfilled shell

Question 6

covalent bonding involves

Answer 6

1 electron from e/ bonding atom of opp. spin

Question 7

formal charge formula

Answer 7

group # - # bonds - # non-bonded electron

Question 8

sp3 hybrids = … (composition)

Answer 8

1x 2s, 3x 2p orbitals (25% s character and 75% p character), sppp

Question 9

what does sp2 have that’s unique (specific orbital)

Answer 9

an unhybridized 2pz orbital that’s perpendicular to the sp2 plane

Question 10

how are sp2 hybridized orbitals oriented

Answer 10

3 sp2 orbitals oriented on a plane, unhybridized 2pz orbital perpendicular to that`

Question 11

sp hybrid structure

Answer 11

1x 2s, 1x 2p with 2 unhybridized 2p orbitals (all perpendicular)

Question 12

constitutional isomers

Answer 12

molecules w/ the same molecular formula but diff bonding

Question 13

nitrile (structure)

Answer 13

C triple bond N

Question 14

organohalide

Answer 14

C-X, X = F, Cl, Br, I

Question 15

inductive effect

Answer 15

difference of electron density in a bond due to differences in EN

Question 16

electrons moving through sigma bonds is called

Answer 16

induction

Question 17

electrons moving through pi bonds is called

Answer 17

resonance

Question 18

types of IMF

Answer 18

dip-dip, H bonding, LDF, electrostatic interactions

Question 19

electrostatic interactions

Answer 19

opp formal charges attracting

Question 20

polar protic solvents

Answer 20

H-bond donors, v polar

Question 21

polar aprotic solvents

Answer 21

mostly H-bond acceptors, strong polar dipoles w/o H bonds

Question 22

non polar solvents

Answer 22

no significant polarity/net dipole

Question 23

degree of unsaturation formula

Answer 23

(2C + 2 - H + V - VII)/2

Question 24

how are ions separated in mass spectrometry

Answer 24

separated based on mass to charge ratio - all ions have the same charge

Question 25

M+ peak?

Answer 25

indicates mass of molecule - it's the highest heaviest peak

Question 26

M+1 peak?

Answer 26

detects heavier isotopes

Question 27

what does spectroscopy measure

Answer 27

interaction b/w a molecule and EM radiation

Question 28

what does infrared spectroscopy measure

Answer 28

bond vibration - stretching, bending

Question 29

(IR spectroscopy) relationship between frequency, strength and mass

Answer 29

inc freq = inc strength = dec mass

Question 30

what types of bonds can absorb IR

Answer 30

polar bonds only (although bonds with slight dipoles still show up on IR)

Question 31

what does intensity of signals on IR tell you

Answer 31

how polar the bonds are

Question 32

what do broad peaks indicate

Answer 32

H bonding

Question 33

which C-C bond is diagnostic

Answer 33

triple bond

Question 34

what is important to note when looking at IR

Answer 34

symmetry around bonds of the molecule (particularly when looking at C-C and C-H bonds)

Question 35

main sections of IR spectrum

Answer 35

hydrogen region, trip bond region, double bond region, fingerprint region

Question 36

what does NMR map

Answer 36

protons/H with unique electronic environments

Question 37

how do neighbouring atoms influence a nucleus's magnetic environment

Answer 37

electron rich nuclei are more shielded and show up at lower ppm, EN atoms deshield H (H close to EN atoms are less e- rich), pi bonds have a deshielding effect (signals will appear more upstream/higher ppm when pi bond exists)

Question 38

what does it mean to be on the left side of the NMR

Answer 38

close to EN atoms and whatnot

Question 39

integration spectrum

Answer 39

ratio of # of H at e/ signal

Question 40

torsional strain

Answer 40

repulsion b/w neighbouring substituents (staggered vs eclipse conformation)

Question 41

steric strain

Answer 41

repulsion from when atoms that are not bonded to e/o are forced to be close to one another - ie large groups too close to e/o (anti vs gauche)

Question 42

angle strain

Answer 42

arise from bond angles that don't permit max orbital overlap b/w atoms of a molecule (ideal is 109.5)

Question 43

1-3 diaxial strain is a type of ...

Answer 43

steric strain

Question 44

stereoisomers (types, \_/ vs \_\)

Answer 44

cis vs trans

Question 45

steric strain vs torsional strain

Answer 45

torsional strain is from overlapping substituents, steric is from BIG overlapping substituents