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85 Cards in this Set
- Front
- Back
What is the IR frequency for C-H?
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2800-3000/cm
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What is the IR frequency for C-C?
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1200/cm
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what is the IR frequency for C=C?
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1645/cm
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What is the IR frequency for C(triple bond)C?
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2200/cm
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What is the IR frequency aromatic hydrogens?
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2900-3100/cm
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What is the IR frequency for alcohols (OH bond)?
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3100-3500/cm broad
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What is the IR frequency for the C--O bond in ethers?
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1050-1150/cm
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What is the IR frequency for the C--H bond in aldehydes?
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2700-2900/cm
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What is the IR frequency for C=O?
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1750
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What is the IR frequency for the N--H bond in amines?
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3100-3500/cm
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What happens to nuclei when placed in a magnetic field?
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their magnetic moments aligh with or against teh direction of the applied field
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An alpha state indicates ____ alignment with the field while beta state indicates _____ alignment with the field.
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parallel; antiparallel
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In the NMR spectrum, frequency (increases/decreases) toward the right and magnetic field (increases/decreases) toward the right.
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decreases; increases
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When a nucleus is deshielded, what occurs?
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An electronegative atom will pull away the electron cloud from the nucleus
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What is the NMR shift for:
RCH3 RCH2 R3CH HC=CH CHX CHOH/CHOR H-CCOOH COO-H NH2 |
0.9
1.25 1.5 4.6-6 2-4.5 3.4-4 2-2.6 10.5-12 1-5 |
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UV spectroscopy is most useful in studying...
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double bonds or hetero atoms with lone pairs
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In mass spectroscopy, the cation radical splits up; which shows up on the spectrum?
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the cation because it is deflected by the magnetic field
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T/F: Carbohydrates are aldehydes/ketones with many hydroxyl groups.
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True.
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All amino acids in our bodies are (L/R) enantiomers.
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L
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All amino acids are chiral except for:
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glycine
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Amino acids have a basic and acidic group and can sometimes form:
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zwitterons
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T/F: amino acids are amphoteric.
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true
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At a high pH, an AA carries an excess ___ charges and at low pH an excess ____ charge.
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negative; positive
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In titrating an amino acid with a base, which group will be first deprotonated?
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carboxyl, then amino group
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In order to deprotonate one mole of amino acids, how many moles of base must be used?
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2 moles; one to deprotonate the carboxyl and the other to deprotonate the amino group
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When is the buffering capacity of an amino acid the greatest?
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near Ka1 or Ka2
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When is the buffering capacity of an amino acid the lowest?
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at the isoelectric point, pI
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What are the characteristics of nonpolar amino acids?
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-have R groups that are saturated hydrocarbons and hydrophobic, decreasing solubility of AA in water; usually found in PM phospholipid bilayer
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What are the characteristics of polar amino acids?
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They have polar, uncharged R groups and are soluble in water.
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What are the characteristics of acidic amino acids?
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R group contains a carboxyl
have a net negative charge exist in salt form in body important role in enzyme binding |
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How many distinct pKa's do acidic amino acids have?
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3
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Is the pI for acidic amino acids closer to an acidic pH or basic pH?
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acidic pH
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What are the characteristics of basic amino acids?
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R group contains an amino group
carry net positive charge pI shifted toward basic pH have 3 pKb's |
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Amino acids are joined by_____ between the _______.
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peptide; carboxyl and amino groups
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The peptide bond is formed via a____ reaction
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condensation
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Primary Structure
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sequence of amino acids
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Secondary Structure
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local structure of neighboring AA's; alpha helix and beta sheet
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Tertiary Structure
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3D shape of protein
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What are disulfide bonds?
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Disulfide bonds create loops in protein chain; two cysteine molecules become oxidized to form cystine
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What is the difference between a fibrous protein and a globular protein?
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fibrous proteins are found as sheets or long strands, while globular are spherical in shape
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In protein tertiary structure, where would one find hydrophilic and hydrophobic groups organized?
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hydrophilic will be on the outside and hydrophobic will be on the inside of the protein
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Quaternary Structure
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how subunits connect to form functioning protein
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Denaturation involves the loss of which protein structure(s)?
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secondary and tertiary
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T/F: IR can tell you what types of bonds are present and how many there are.
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False; IR cannot tell you how many bonds there are
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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.
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low; high
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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 ______.
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1-5; 5-10
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UV visible spectroscopy is best used to examine:
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conjugated systems
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The base peak in mass spectroscopy is the most ________ ion.
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abundant
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Conditions for simple distillation:
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separates liquids that boil below 150C and 25C apart
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Conditions for vacuum distillation:
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separates liquids that boil above 150C and at least 25C apart
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Conditions for fractional distillation:
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separate liquids that boil less than 25C apart
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Silica gel is highly _____ and hydro______.
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polar and hydrophilic
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In TLC, the mobile phase is usually an _______ solvent with _________ polarity.
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organic; weak
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___polar compounds move quickly while _____polar compounds stick to gel.
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nonpolar;polar
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How are the spots of a TLC seen?
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via UV light or I2 stain
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What is the Rf value?
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distance compound travels/distance solvent travels
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How can pure compounds be recovered from silica gel?
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by rinsing with a polar solvent
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What is the adsorbant in:
a. TLC b. CC c. GC |
a. paper
b. silica or alumina c. column |
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Compounds move via ____ in TLC and ____ in CC.
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capillary action; gravity
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What is the most important factor to consider in electrophoresis?
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the size of the molecules
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What is the isoelectric point?
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the pH where the net charge is zero
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What happens to a protein when pH = pI?
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it stops moving
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Isoelectric focusing separates proteins based on:
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charge
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In spectroscopy, for an absorption to be recorded, what must occur?
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a change in bond dipole moment
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What are the solvent requirements for recrystallization?
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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
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What is the main idea behind extraction?
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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
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In extraction, hydrogen bonded compounds will most most easily into the _____ layer.
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aqueous
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T/F: adding a base will help you extract an acid
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True
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What is the main idea behind recrystallization?
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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
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T/F: in recrystallization, the desired product should have solubility that depends on temperature, while the impurities should be equally soluble in all temperatures.
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true
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What is the main idea behind the technique of sublimation?
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impurities do not sublime as easily as the desired product
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What two things can one do to make a solid sublime?
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1. raise the temperature at a low enough pressure
2. lower the pressure at a very cold temperature |
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T/F: centrifugation is used to separate small things from one another
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false; centrifugation is mostly used to separate large compounds from each other based on size such as organelles
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What is distillation?
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separation of one liquid from another through vaporization and condensation
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Is vacuum distillation performed under low or high pressures?
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low, so as to lower the boiling points of liquids and preventing decomposition due to excessive temperature
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T/F: fractional distillation can be thought of as repeated distillation
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true
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Chromatography separates compounds based on their:
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differing chemical properties; based on how strongly they adhere to the solid (stationary) phase
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Why is it imperative that the initial spots of a TLC be above the level of the solvent?
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otherwise, the spots will elute off into teh solvent rather than move neatly up the plate
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T/F: in TLC, the more polar a solvent, the faster the sample will migrate
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true
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What is the main idea behind gas chromatography?
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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
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T/F: In electrophoresis, anions are attracted to the anode, while cations are attracted to the cathode.
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true
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What is the stationary phase in GC?
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the column
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In electrophoresis, what two things can one do to make the gel run faster?
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1. increase the voltage (electric field)
2. use a lower % of agarose or acrylamid (to decrease friction) |
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What is the formula for migration velocity in electrophoresis?
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v = Ez/f; z = net charge of molecule, f = frictional coefficient, E = electric field
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Agarose gel is used to separate ______ while SDS PAGE is used to separate _______.
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nucleic acids; proteins
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