5: Flashcards
what is an spectroscopy?
spectroscopy = use of IR for chemical analysis
when a molec absorbs IR light, excited bonds go from ground state -> excited state
when IR’s v matches to bond vobration’s v,light is absorbed nd molec is vibrationally excited
what is k in the context ofcf harmonic oscillator?
= forcee constant and proportional to the bond strength (stiffness)
larger k (tighter spring) = higher enrgy vibrations’ v
triple ? double > single bond
sp > sp2 > sp3
a value tht compensates for 2 diff mass in harmonic oscillator
μ reduced mass
smaller r μ (lighter atoms) = higher enrgy vibration
how does hybridization affect bond strength?
triple bonds to single
high energy vibration to low
(higher b.o, higher E)
how to differentiate cis / trans cycloalkanes
what is a cycloalkanes?
a ring of C atoms connectd by C-C bonds
roatiohn is hindered
has 2 conformations: chair & boat
alkenes vs alkynes
alkenes: have 1 or more C-C double bonds
alkynes: have 1 or more C-C triple bond
for
what is u in harmonic oscilator?
u = mas difference
smaller u (ligher atom) -> higher energy vibration’ v
T or F
stretching vibration: symmetric and asymmetric
bending vibration: scissoring, rocking, wagging and twisting
T
for IR spectrometry, alcohol will have a small, narrow OH stretch T OR FALSE
fales, broad and strong stretch
what is constitutional isomer?
= molecular formula, bt diff in atom connectivity
alkane: CnH2n+2
alkene + cyclic ring: CnH2n
conformer?: staggered and eclipsed?
= non-permanent spatial arrgn. of atoms by caused by rotating single bonds
eclipsed: C-H bonds are in line, less stable, higher in E
staggered: diff, less repulsionl. more stable, lower in E
anti vs gauche
anti is stagged conformer lowest in E (Cl-Cl top to bottom)
gauche is staggered conformer higher in E than anti (to the side)
