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85 Cards in this Set

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  • Back
What is the IR frequency for C-H?
What is the IR frequency for C-C?
what is the IR frequency for C=C?
What is the IR frequency for C(triple bond)C?
What is the IR frequency aromatic hydrogens?
What is the IR frequency for alcohols (OH bond)?
3100-3500/cm broad
What is the IR frequency for the C--O bond in ethers?
What is the IR frequency for the C--H bond in aldehydes?
What is the IR frequency for C=O?
What is the IR frequency for the N--H bond in amines?
What happens to nuclei when placed in a magnetic field?
their magnetic moments aligh with or against teh direction of the applied field
An alpha state indicates ____ alignment with the field while beta state indicates _____ alignment with the field.
parallel; antiparallel
In the NMR spectrum, frequency (increases/decreases) toward the right and magnetic field (increases/decreases) toward the right.
decreases; increases
When a nucleus is deshielded, what occurs?
An electronegative atom will pull away the electron cloud from the nucleus
What is the NMR shift for:
UV spectroscopy is most useful in studying...
double bonds or hetero atoms with lone pairs
In mass spectroscopy, the cation radical splits up; which shows up on the spectrum?
the cation because it is deflected by the magnetic field
T/F: Carbohydrates are aldehydes/ketones with many hydroxyl groups.
All amino acids in our bodies are (L/R) enantiomers.
All amino acids are chiral except for:
Amino acids have a basic and acidic group and can sometimes form:
T/F: amino acids are amphoteric.
At a high pH, an AA carries an excess ___ charges and at low pH an excess ____ charge.
negative; positive
In titrating an amino acid with a base, which group will be first deprotonated?
carboxyl, then amino group
In order to deprotonate one mole of amino acids, how many moles of base must be used?
2 moles; one to deprotonate the carboxyl and the other to deprotonate the amino group
When is the buffering capacity of an amino acid the greatest?
near Ka1 or Ka2
When is the buffering capacity of an amino acid the lowest?
at the isoelectric point, pI
What are the characteristics of nonpolar amino acids?
-have R groups that are saturated hydrocarbons and hydrophobic, decreasing solubility of AA in water; usually found in PM phospholipid bilayer
What are the characteristics of polar amino acids?
They have polar, uncharged R groups and are soluble in water.
What are the characteristics of acidic amino acids?
R group contains a carboxyl
have a net negative charge
exist in salt form in body
important role in enzyme binding
How many distinct pKa's do acidic amino acids have?
Is the pI for acidic amino acids closer to an acidic pH or basic pH?
acidic pH
What are the characteristics of basic amino acids?
R group contains an amino group
carry net positive charge
pI shifted toward basic pH
have 3 pKb's
Amino acids are joined by_____ between the _______.
peptide; carboxyl and amino groups
The peptide bond is formed via a____ reaction
Primary Structure
sequence of amino acids
Secondary Structure
local structure of neighboring AA's; alpha helix and beta sheet
Tertiary Structure
3D shape of protein
What are disulfide bonds?
Disulfide bonds create loops in protein chain; two cysteine molecules become oxidized to form cystine
What is the difference between a fibrous protein and a globular protein?
fibrous proteins are found as sheets or long strands, while globular are spherical in shape
In protein tertiary structure, where would one find hydrophilic and hydrophobic groups organized?
hydrophilic will be on the outside and hydrophobic will be on the inside of the protein
Quaternary Structure
how subunits connect to form functioning protein
Denaturation involves the loss of which protein structure(s)?
secondary and tertiary
T/F: IR can tell you what types of bonds are present and how many there are.
False; IR cannot tell you how many bonds there are
In NMR, a nucleus aligned with the field is in a (low/high) energy state while one aligned opposite is in a (low/high) energy state.
low; high
For NMR, if a H is bonded to an sp3 carbon, the shift will be b/w _____ and if it is attached to an sp2 carbon, the shift will be b/w ______.
1-5; 5-10
UV visible spectroscopy is best used to examine:
conjugated systems
The base peak in mass spectroscopy is the most ________ ion.
Conditions for simple distillation:
separates liquids that boil below 150C and 25C apart
Conditions for vacuum distillation:
separates liquids that boil above 150C and at least 25C apart
Conditions for fractional distillation:
separate liquids that boil less than 25C apart
Silica gel is highly _____ and hydro______.
polar and hydrophilic
In TLC, the mobile phase is usually an _______ solvent with _________ polarity.
organic; weak
___polar compounds move quickly while _____polar compounds stick to gel.
How are the spots of a TLC seen?
via UV light or I2 stain
What is the Rf value?
distance compound travels/distance solvent travels
How can pure compounds be recovered from silica gel?
by rinsing with a polar solvent
What is the adsorbant in:
a. TLC
b. CC
c. GC
a. paper
b. silica or alumina
c. column
Compounds move via ____ in TLC and ____ in CC.
capillary action; gravity
What is the most important factor to consider in electrophoresis?
the size of the molecules
What is the isoelectric point?
the pH where the net charge is zero
What happens to a protein when pH = pI?
it stops moving
Isoelectric focusing separates proteins based on:
In spectroscopy, for an absorption to be recorded, what must occur?
a change in bond dipole moment
What are the solvent requirements for recrystallization?
the solvent must dissolve the purity at high T but not at low T; it must dissolve the impurity at both high and low T
What is the main idea behind extraction?
transfer of a dissolved compound from one solvent into another in which it is more soluble; most impurities are left behind in the first solvent; the two solvents should be immiscible; more product can be obtained with more extractions
In extraction, hydrogen bonded compounds will most most easily into the _____ layer.
T/F: adding a base will help you extract an acid
What is the main idea behind recrystallization?
impure crystals are dissolved in a mimimum amount of hot solvent; as the solvent cools, the pure crystals reform; the solvent must be able to dissolve the desired product at high temperature but not at low; and it must be able to dissolve the impurities at both temperatures
T/F: in recrystallization, the desired product should have solubility that depends on temperature, while the impurities should be equally soluble in all temperatures.
What is the main idea behind the technique of sublimation?
impurities do not sublime as easily as the desired product
What two things can one do to make a solid sublime?
1. raise the temperature at a low enough pressure
2. lower the pressure at a very cold temperature
T/F: centrifugation is used to separate small things from one another
false; centrifugation is mostly used to separate large compounds from each other based on size such as organelles
What is distillation?
separation of one liquid from another through vaporization and condensation
Is vacuum distillation performed under low or high pressures?
low, so as to lower the boiling points of liquids and preventing decomposition due to excessive temperature
T/F: fractional distillation can be thought of as repeated distillation
Chromatography separates compounds based on their:
differing chemical properties; based on how strongly they adhere to the solid (stationary) phase
Why is it imperative that the initial spots of a TLC be above the level of the solvent?
otherwise, the spots will elute off into teh solvent rather than move neatly up the plate
T/F: in TLC, the more polar a solvent, the faster the sample will migrate
What is the main idea behind gas chromatography?
a mixture is injected into a column and vaporized; the gaseous compounds will travel through column at different rates, and a detector will detect each one at the end of the tunnel
T/F: In electrophoresis, anions are attracted to the anode, while cations are attracted to the cathode.
What is the stationary phase in GC?
the column
In electrophoresis, what two things can one do to make the gel run faster?
1. increase the voltage (electric field)
2. use a lower % of agarose or acrylamid (to decrease friction)
What is the formula for migration velocity in electrophoresis?
v = Ez/f; z = net charge of molecule, f = frictional coefficient, E = electric field
Agarose gel is used to separate ______ while SDS PAGE is used to separate _______.
nucleic acids; proteins