CHM 244 final….LAST ONE

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anthocyanin
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water-soluble, acid-stable, colored pigments found in the vacuole of plants
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substituents to anthocyanins
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hydroxy and/or methoxy substituents present on all three rings, hydroxy are modified by glycosidic linkages or acetyl groups
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anthocyanidins
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algycosidic form of anthocyanin, readily formed by acid-catalyzed hydrolysis
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color of anthocyanin and anthocyanidin
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pH dependent
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flavylium content
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extended pi conjugation through all rings which is why the rage appears longer
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when does color disappear?
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as pH of solution increases
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what must the solution be to maintain colored form of anthocyanins?
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acidic
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why use reflux condenser and hot plate
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thermally drive hydrolysis rxn
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reflux
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constant temperature
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condenser
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keeps solvent from evaporating
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cellulose chromatography paper
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linear polymer with glucose linkages, makes polar surface
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how will substances partition on chromatography paper?
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btwn the stationary and mobile phase based primarily on over all polarity with less polar materials spending more time in less polar mobile phase meaning lower Rf
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polar solvent
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alcohols, carboxylic acids, and water
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whats new about this chromatography?
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both stationary and mobile phases are polar so they will partition based on specific individual interaction between the substances and the two phases
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anthocyanin and chromatography
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ability of glycosidic side chains to interact with the cellulose fibers
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anthocyanidin and chromatography
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no glycosidic side chain so H-bonding will play an important role
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hydroxy substituent
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decreased mobility compared to a methoxy substituent or H
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highly conjugated species
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anthocyanin and anthocyanidins have HOMOs and LUMOs so promotion of e- from one tot the other requires light energy
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light that is absorbed
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complementary to the color that we see with our eyes
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Beer’s law
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relate absorbance of molecule to its concentration
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molar absorptivity
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intrinsic property measures the probability of an electron transition, larger it is the more probable the electronic transition
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ABTS+
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ABTS with potassium sulfate
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when antioxidant is added to ABTS+ solution
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radical abstracts hydrogen from the antioxidant and a positively charged and colorless form of the radical cation
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extent and rate of decolorization of ABTS+
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related to the antioxidant strength of the extract
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supernatant
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liquid of berry extract
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distillation
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separation and purification technique that separates components from liquid mixtures on their vapor pressure
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components in distillation
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purify by going from liquid to gas phase, must have appreciable vapor pressures at temperatures below the decomposition points
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calculations for pressure
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pressure and composition of a vapor above an ideal picture of liquids can be calculated based on Raoult’s or Dalton’s laws
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Raoult’s law
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sum of vapor pressures of individual components
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most distillation techniques rely on what?
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substance with the greatest vapor pressure will be enriched in the vapor phase in equilibrium with a boiling liquid phase containing a mixture of substances
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condensation of vapor phase
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leads to sample containing greater proportion of more volatile component
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simple distillation
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liquid vapor equilibrium occurs once, leads to partial separation of two volatile components
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fractional distillation
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series of liquid-vapor equilibria that may lead to efficient separation of mixtures of two volatile materials
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how is separation achieved in fractional distillation
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vapor component becomes the liquid component for the next equilibrium, as each is established it becomes successively more enriched with more volatile component
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vacuum distillation
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atmospheric pressure above the liquid is reduced by applying a vacuum, mixture boils at a lower temperature to avoid decomposition
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rotary evaporation
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isolate non-volatile materials by rapidly distilling the volatile solvents away under reduced pressure
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steam distillation
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used when materials that need to be purified are immiscible in water
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total pressure above the mixture of water and immiscible liquid
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Pt=Pa+Ph2o
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Pt
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atmospheric pressure, distillation occurs at temp under 100 because total pressure of mixture depends on the vapor pressure of both water and immiscible liquid
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boiling point of mixture and boiling point of pure water
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1-4 degrees lower
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mole fraction of immiscible liquid
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0.03-0.15
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essential oils
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water-insoluble volatile natural product mixtures obtained from plant resources
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what are anethole, cinnamaldehyde and eugenol characterized by?
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aromatic ring with an unbranched 3-carbon side chain
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what are linalool and carvone characterized by?
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five-carbon isoprene unit by metabolic pathways involving pyrophosphate and dimethylallyl pyrophosphate
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stereoisomerism
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arise from presence of chirality centers
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stereocenters
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atom at which the exchange of two substituents will generate a stereoisomer
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sp2 carbons of E and Z alkenes
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stereo centers but not chirality centers
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how to determine major component of oil in sample?
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the spot closest to the standard oil spot will be the major component because it was the target of the distillation
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ambiguities in TLC plate
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steam distillation usually does not pull only target out so won’t be as pure as fractional, seen in different Rf values of the standard and experimental
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how to determine if there are other components in oils based on Rf values
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if the Rf values are similar to another sample oil, then it might have that one in it
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why is Sn2 useful?
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allows for displacement of good leaving groups, by a wide variety of nucleophiles, stereochemistry is predictable, reaction occurs without rearrangement to carbon skelton
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stereochemistry prediction
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inversion of stereochemistry, very stereo specific
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good leaving groups
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halides, tosylates, mesylates, diazo groups
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nucleophiles
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Lewis bases
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if second Sn2 reaction occurs
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stereochemistry will be inverted a second time leading to overall retention of configuration
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alpha- amino acid
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poor leaving group but can be converted into good leaving group, N2, by diazoation reaction
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method 1
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involves double Sn2 displacement that proceeds via intramolecular reaction
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Method 2
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proceeds via a single Sn2 displacement
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intermolecular
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occurs between nucleophile and electrophile substrate that are on two different molecules
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intramolecular
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Sn2 reaction can occur if nucleophile and electrophile are part of same molecule, much faster than intermolecular
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in this case
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diazoated alpha amino acid, the intramolecular nucleophile is the oxygen of the carboxylic acid, leading to highly reactive alpha lactone
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melting point of racemic mixture
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different from either pure enantiomer, lower
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[alpha]
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specific rotation, intrinsic property, greater concentration or path length will lead to grater measured rotation angle
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l
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path length
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alpha
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observed rotational angle
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c
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concentration
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larger concentration of sample
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more accurate measurement of specific rotation
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L-entatiomer
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D-enantiomer
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+
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what data shows that rxn proceeded in a stereospecific manner?
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melting points were different meaning the experimental sample was not the D-phenyllactic acid enantiomer, otherwise the two melting points would be the same because it would only be D-phenyllactic acid
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start with which enantiomer?
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L-phenylalanine
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what helped determine the absolute configuration of phenyllactic acid?
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polarimetry, specific rotation was calculated, it was a negative rotation in acetone, final sample was L-phenyllactic acid
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phenylalanine to phenyllactic acid?
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NH2–>OH
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absolute configurations of phenylalanine and phenllyactic acid
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both were S, retention of configuration, two step consecutive displacement method
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why is phenylalanine soluble in acidic rxn mixture while phenyl lactic acid is not?
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phenylalanine can act as acid or base while phyllactic acid cannot because it only has OH functional groups, phenylalanine has both OH and NH2
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[alpha] calculation
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(alpha sample-alpha blank)/L*c
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vitamin A different states
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alcohol retinol, aldehyde retinal, carboxylic acid retinoic acid (RA)
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RA similar structures
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cyclic hydrophobic end group connected to polyene chain that terminates in a polar end group, usually carboxylic acid
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substitution rxn that happens in Sn1
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2,5-dimethyl-2,5-hexanedoil into 2,5-dichloro-2,5-dimethylhexane
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concentrated HCl in Sn1
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protonation of OH is first step then carbocation can be attacked by any nucleophile species in solution, since HCl is in high concentration and it’s a better nucleophile that water, it will be favored
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if sample melting point is lower than accepted melting point
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there were impurities in it
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using IR to determine purity
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if there were any peaks that look like initial sample, then it is has some impurities
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highest concentration of anthocyanin
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blueberries
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glycosidic side chains interaction in chromatography
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interacted more with less polar mobile phase, side chains were making anthocyanins more polar than anthocyanidins
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why did two eluting systems produce different results?
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they had differing polarities, butanol has higher polarity than formic acid and could better demonstrate the differences in polarity

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