uworld orgo Flashcards
the compound 4-nitrophenol contains all of the following in its infrared spectrum except
N-H stretch
IR spectrum of a compound indicates
the types of bonds and functional groups present in a compound
different functional groups absorb
IR radiation at diff frequencies
signal from each group appears in a
particular region of the IR spectrum
individual molecules may have distinct absorption spectra in the fingerprint region (700-1500 cm-1)…
each func group on the molecule will still absorb in its characteristic IR region
4-nitrophenol contains
hydroxyl group (-OH)
aromatic ring
nitro groups (-NO2)
no N-H bonds –> no N-H stretch
functional group bands appear in the
same region of the IR spectrum regardless of molecule’s overall structure
distillation is a
purification technique that separates molecules based on boiling point
a liquid mixture is heated to a temp that overcomes the
intermolecular forces keeping the compound in the liquid phase
vapors condense in the collection flask as a liquid
molecule that dissipates in strong IM forces will have a higher or lower boiling pt?
a higher boiling point
hydrogen bonding can be
intermolecular
intramolecular
constitutional isomers can have different
boiling points due to difference in connectivity and that they experience different IM forces
parasubstituent
1,4 relationship
ortho substituent
1,2 relationship
hydroxyl and nitro groups on 4-nitrophenol are…
para
because of para hydroxyl and nitro groups on 4-nitrophenol, they are able to
H bond intermoleculary not intramolecularly
intermolecular bonds hold molecules of 4-nitrophenol together, thereby..
increasing the boiling pt and causing i.t. to stay in the flask while the 2-nitrophenol distills
superheating occurs when
a liquid is heated above its boiling pt but does NOT boil
what can cause superheating?
surface tension - it inhibits formation of bubbles
when bubbles attempt to form during superheating…
surface tension causes a local increase in vapor pressure
vapor pressure > ambient pressure
liquid heats beyond boiling pt
bumping is
the formation of large bubbles at the surface that erupt and eject the hot liquid from the flask
consequence of bumping
difficult to overcomes without damage to the flask
boiling chips are made of
nonreactive porous materials + provides nucleation sites
nucleation sites
divots on surface of boiling chip
boiling chips facilitate the
even boiling of water in the flask
prevents superheating
what technique could monitor the formation of 4-aminophenol by excitation of electrons w/ high energy photons?
TLC
thin layer chromatography (tlc)
monitors reactions
what can be used to visualized results from TLC?
UV light but only if the reaction mixture can absorb the UV light
UV light carries a large amount of
energy that excites electrons of UV chromophores to a higher E state
UV chromophores includes
double and triple bonds
carbonyls (C=O)
nitroso groups
alkyl halides
conjugated systems
aromatic ring in the starting material of the rxn (4-nitrophenol) and the product (4-aminophenol) is a
UV chromophore
each compound can absorb UV light and appears on TLC place
in mass spectrometry, a sample is
ionized by high energy electrons
electrons do not change E levels
an external magnetic field is applied to a sample in
NMR spectroscopy
radio waves are used to
detect H atoms and excite them from the alpha-spin to the beta spin state
radio waves are low in E
gas chromatography requires
vaporization of a sample (phase change)
not an electronic excitation
Rf =
distance compound traveled from origin / distance from origin to solvent front
TLC is a technique used to
separate compounds based on polarity
mobile phase
organic solvent travels up the stationary phase via capillary action
stationary phase
a thing absorbent place coated w/ silica
low capillary action
low adhesive forces on top > high adhesive forces
more capillary action
low cohesive forces on bottom > high adhesive forces on top
components of a mixture travel up the plate at
different rates b/c of varying polarity
in normal TLC, nonpolar compounds travel
further up the plate
have less affinity for the polar stationary phase
Rf value is always
less than 1
smaller Rf =
more polar, less mobile compounds
amide has more
H bond accepts
amine is a
H bond donor and acceptor via only one electronegative atom (N)
amide is a
H bond donor and acceptor via two electroneg atoms (O and N)
O-H stretch (phenol)
3650-3200 cm-1
C-C stretch
1600-1475 cm-1
sp2 C-H stretch
3100 cm-1
NH stretch (amide)
3550-3060 cm-1
C=O stretch (amide)
1650 cm-1
sp3 C-H stretch
3000 cm-1
acetaminophen contains several functional groups including
phenol (hydroxyl group)
aromatic ring
amide (strong absorption in IR spectrum)
carbonyl (C=O) group from an amide shows an absorption from
1690-1650 cm-1
