Org 1 lab final Flashcards
Important properties of a solvent for recrystallization(3)
-not react with compound
-dissolve compound when hot, but not when cold
-dissolve all impurities at all temps or never dissolve any
what solvent and solid is recrystallization favored for
-high melting solvent
-thermally unstable solid
should you use a warm or cold rinse on crystals
cold or they will dissolve
is the stationary phase of TLC polar or non-polar
polar
describe the stationary phase for TLC
silica gel on a solid backing
is the mobile phase of TLC polar of non-polar
non-polar
describe the mobile phase of TLC
solvent mixture carries compounds across stationary phase
what determines how far a compound travels on TLC sheet
polarity, the more polar the farther it travels, greatest difference in polarity get best results(too polar may go too far)
what information do you get from an IR spectra
what functional groups are present on a molecule
what must be present for change on IR to occur(stretch, twist, etc)
bond dipole
what IR region is relative to visible light
red
which has more energy: bend or stretch (IR)
Stretch
which groups are more than 3000 on IR spectra
nitrile
ketones
ester
alkene
what methods does distillation use to purify? how does it purify?
heating and cooling
separate mixtures by vaporization point(different boiling points)
T/F more plates/fractions in distillation give you a more pure product
TRUE
how many theoretical plates is equal to a simple distillation
one
T/F as the difference in boiling point decreases the number of theoretical plates for purification increases
TRUE
Ex. 4 degrees needs 65 plates
35 degrees needs 5 plates
describe the stationary phase of distillation
inert carrier gas
describe mobile phase of distillation
carrier gas and compound run via packed column
what factors affect boiling point
-IMFs
-# of carbons in chain
-branching
how does # of carbons affect boiling point
as carbon # decreases, BP decreases
how does branching impact boiling point
Increased branching = decreased BP
how do intermolecular forces impact boiling point
ionic>H bonding>D-D>london dispersion
higher BP Lower BP
T/F enantiomers CAN be separated through simple distillation
FALSE
T/F constitutional isomers CAN be separated through simple distillation
TRUE, branching changes BP
what does the organic phase dissolve
organic substances
what does the aqueous phase dissolve
organic and inorganic salts
T/F aqueous phase is always the bottom layer
FALSE, position depends on density, most organic layers are less dense than water, but not always
what organic phases are more dense than water
-DMSO
-CH2Cl2
how do you fix emulsion during extraction
add water and shake gently
how to tell which phase(organic or aqueous a compound/solvent will be in)
organic
-non-polar
-basic(can move into aqueous)
-neutral substances
Aqueous
-polar
-acid
what reaction was used for phase transfer catalyst
Williamson ether synthesis
what causes unwanted peaks in an IR spectra
unreacted starting material or impurities
definition of solvolysis
solvent acts as reagent(nucleophile) in reaction
what increases rate of reaction and stability in solvolysis
-double bonds
-ability to form resonance structures
what is the rate-determining step of solvolysis
formation of carbocation
what reaction type is dehydration of cyclohexanol
E1
what is an azeotrope
mixture of 2+ liquids that have a single sharp boiling point
properties of azeotrope
-single boiling point lower than individual BPs
-compounds will vaporize together even if individual BP are different
-cyclohexanol/water will distill at 98C
-cyclohexene/water will distill at 71C
explain bromine test
add 2 Br in anti positions
how to calculate percent yield
(actual yield/theoretical yield) x 100
how to calculate theoretical yield
multiply moles by molar mass
what is a theoretical plate
one vapor condensation event
what stretch/bend does water have
-Bend
-asymmetrical stretch
-symmetrical stretch
fine vs. rough melting point
rough: temp rise 6-10C/min
fine: temp rise 1-2C/min
how do impurities impact melting point
lowers and broadens melting point
what is the point of chromatography
to monitor a reaction
what types of stretch are there
symmetrical
asymmetrical
what types of bend are there
twisting
wagging
rocking
scissoring
where is the fingerprint region, what info does it give
-1400-14 cm-1
-tells about exact structure of molecule(don’t usually pay attention to)
what is shown at the top of a peak on a gas chromatography chart
time it took for compound to pass through column
what does it mean if a compound has a lower time on a GC chart
it vaporizes more quickly
what does the area under a peak on a GC chart indicate
how much of a certain compound is present
how does extraction use the organic and aqueous phase to separate two liquids
react one liquid so it can pass between the phases
when is it important to check the fingerprint region
if looking for an ether
(phase transfer catalysis experiment)
T/F in Sn1 solvolysis water can attack from either side and will form two stereoisomers/a racemic mixture
TRUE
how to calculate Rf
dist. spot traveled/dist. solvent traveled
first order reaction formula
rate=k[substrate]
what impacts the rate determining step in Sn1 solvolysis
polarity of solvent
