MCAT chem/phys

Give the definition for enantiomers. What is there R/S configuration?

non-superimposable mirror images that canNOT appear identical with rotation.

• >1 chiral center

• NO internal plane of symmetry

• opposite R/S configuration

give the definition for diastereomers.

Non-super imposable MIRROR images, NOT mirror images

• >2 chiral centers

• some opposite and some same R/S configuration

what is the difference between constitutional isomers and steroisomers?

• Consitutional isomers have DIFFERENT connectivity

• stereoisomers have the same connectivity but DIFFERENT spatial arrangements

• They both have the same molecular formula.

What are the differences between diastereomers and enantiomers?

• Enantiomers are mirror images

• enantiomers have all opposite R/S configurations at chiral centers. diastereomers have some same, some different.

For Poiseuille’s Law give the relationship between flow rate and each of the variables (how do changes in each variable effect Q)

• Q is proportional to r^4 (double r= increase Q by 16x)

• Q=P, more pressure difference = more flow

• Q=1/viscosity (double viscosity = ½ flow)

• Q= 1/L (double length = ½ flow)

what is the difference between heat capacity and specific heat?

• heat capacity: the amount of heat required to raise the temperature of an object by 1 deg C

• specific heat: the amount of energy required to raise the temperature of 1 gram of the substance by 1 deg C

What is hyperopia and what causes it? Where is the original image? What lens is used to fix this and how does it work?

hyperopia = farsighted

• optical power is not sufficient → image is BEHIND retina

• tx w/ converging/convex lens → focal point shifted toward the retina

What is myopia and what causes it? Where is the original image? What lens is used to fix this and how does it work?

myopia = nearsighted

• focal point is in FRONT of retina

• tx with diverging/concave lens → shift image away from lens

converging/convex lenses create what type of image?

real and inverted

diverging/concave lenses create what type of image?

virtual and upright

what type of wave is light?

a transverse electromagnetic wave

what does it mean for a wave to be “transverse”?

the wave oscillates perpendicular to the direction of travel

give a one-sentence definition of polarization:

restricting in the electric field of a transverse wave to one direction (unpolarized light usually goes in many directions)

• one direction of oscillation

why can light waves be polarized but not sound waves?

sounds waves are longitudinal, light waves are transverse

what 2 fields make up light?

magnetic field (B) and electric field (E)

which field of light determine polarization?

E (electric) field

what does a linear polarization filter do to light?

allows for transmission of electromagnetic radiation whose E field is parallel to the axis of polarization.

• inhibits passage of radation whose E field is perpendicular to this axis

what happens to the intensity (I) of unpolarized light if it passes through ONE polarizer?

Intensity becomes ½ of its original

what happens if light hits 2 polarizers at 90 degrees?

NO light passes

what does polarization ALWAYS refer to?

direction of E field

In normal TLC the stationary phase is ______ and the mobile phase is _______

stationary: polar (silical gel, alumina)

mobile phase: nonpolar (hexanes, ethyl acetate)

In normal TLC:

nonpolar compounds will react more strongly with the stationary/mobile phase and procees closer to/farther from the solvent front.

polar compounds will react more strongly with the stationary/mobile phase and proceed closer to/farther from the solvent front.

• nonpolar compounds react more w/ the mobile phase because it is nonpolar (like dissolves like) and therefore proceeds closer to the solvent front.

• polar compounds react more w/ the stationary phase because it is polar and therefore be farther from the solvent front

which types of compounds (polar/nonpolar) will have a larger Rf in TLC?

nonpolar, because they interact more with the nonpolar mobile phase and move farther down the plate towards the solvent front

What are the 5 steps for balancing a chemical equation? (non redox)

1. Determine what rxn is occuring (reactants, products, physical states, etc.)

2. Write unbalanced equation

3. Balance 1 atom at a time: Start with substance with most elements present

4. Small whole # coefficients: resolve fractional coefficients by multiplying by a factor

5. Check each atom to ensure equation is balanced.

What are the steps for balancing a redox rxn chemical equation?

1. Separate rxns (ox/red): Divide rxn into oxidation and reduction rxns

2. Balance elements: other than O or H first. Then add H2O or H+ as needed (Double check to see if rxn is occuring under ACIDIC (H+) or BASIC (OH-) conditions)

3. Balance charge: Add e- to balance charge. Multiply each half-equation by an integer so the number of electrons in each equation is equal. Make sure you multiply every term in the equation by this integer.

4. Combine half rxns: Add the two half equations together. Cancel and simplify terms that appear on each side

What is the avg molecular wt. of an AA? How can you calculate the molecular wt of a polypeptide?

Avg wt. AA = 110 kDa

Avg wt. polypeptide = # AAs x 110 kDa

What is the oxidation # for Group 17 (halogens)?

-1 unless bonded to a more EN atom (ex: Cl= +1 when HOCl)

What are the oxidation #s for Group 1 metals (alkali metals) and Group 2 metals (alkaline earth metals)?

Group 1 (alkali): +1

Group 2 (alkaline earth): +2

What are the oxidation #’s of Ag, Cd, Zn, Ga, and Al?

Ag = +1

Cd = +2

Zn = +2

Ga = +3

Al = +3

What is the oxidation # for H?

+1 UNLESS bonded to < EN metals from group 1 or 2 (ex: H= -1 when NaH)

What is the oxidation # for O?

2-

what are the 4 steps for IUPAC naming?

1. Select parent chain

2. Number the chain based on priority of fxnl groups

3. Name substituents

4. Assign numbers to substituents

5. Complete names

How do you select the parent chain when IUPAC naming? What do you do if there is a tie between options?

• longest C chain = parent chain

• IF TIE → chain with greatest # of substituents wins

How do you number the substituents on the parent chain when IUPAC naming? (hint: which # should the highest priority fxnl group have)

• Highest priority fxnl group = LOWEST possible #

• If subs have = priority → all as low # as possible

From highest to lowest priority, list the priority of all fxnl groups when following IUPAC naming.

COOH > anhydrides > esters > amides > aldehydes > ketones > alcohols > alkenes > alkynes > alkanes

How do you name C substituents off of the parent chain? what do you do if there are multiple substitutents of the same type?

• Prefix (meth/eth/prop/but/etc.) + -yl

• multiple subs of same type → use prefixes (di-, tri-, etc.)

List the prefixes and suffixes for all functional groups from highest to lowest priority.

COOH: carboxy—, —oic acid

anhydride: alkanoyloxycarbonyl—, anhydride

ester: alkoxycarbonyl—, —oate

amide: carbonoyl—/amino—, —amide

aldehyde: oxo—, —al

ketone: oxo—/keto—, —one

alcohol: hydroxy—, —ol

alkene: alkenyl—, —ene

alkyne: alkynyl—, —yne

alkane: alkyl—, —ane

Give the approximate equivalents for the following fractions:

3/2, 9/2, 1/5

3/2 = 1.5

9/2 = 4.5

1/5 = 0.2

Elements with > ionization energy typically have > EN except for which 3 elements?

He, Ne, Ar

when a metal is binding into coordinate covalent bond, which orbital do the non-metal e- bind into?

non-metal e- are binding into free d orbital

If given the known mass of each element in a compound, how can you determine the empirical formula? (2 steps)

1. determine the # of moles of each element (by dividing the known mass by its molar mass)

2. Divide the each molar amount by the smallest molar amount to find the relative ratios of each type of atom

How do you find the molecular formula of an element when given the empiricial formula and the molecular wt?

Find the molecular wt of the empirical formula then multiply the each element in the empirical formula until the molecular wt matches that of the problem.

• ex: if the MW is double that of the given wt of the empirical formula, you must double the number of each of the elements to find the molecular formula

Provide the resonance frequency and characteristics on IR spectroscopy for carbonyls, nitriles, carboxylic acids, Amines/amides, and alcohols?

• Carbonyl (C=O): 1700, sharp and deep

• nitriles (CN, triple bond): 2250, sharp and deep

• COOH (OH*): 3000, broad

• Amine/Amide (NH): 3300, BOTH broad

  • amine → shallow

  • amide → deep

• alcohol (OH): 3300, broad

What type of bonds are shown at locations A and B on this IR spectroscopy?

• A: O-H in a COOH

  • 3000

  • broad

• B: C=O

  • 1700

  • sharp and deep

Identify which peak (A or B) in this IR spectroscopy is an amide and which one is an amine. How do you know?

NH Bond: Amide/Amines, 3300, Broad and looks like a W

A: AMIDE because the peaks are DEEP

B: AMINE, same thing but shallow

**DO not confuse these with CH bonds, CH bonds are at a lower frequency than 3300**

What are the 2 types of gel electrophoresis? How do they differ in separating particles?

1. Native Gel: separates by charge AND size

2. SDS Page: separates by size ONLY; molecules are coated in NEG charge so everything is the same charge **NOTE: everything is denatured in SDS page**

What is isoelectric focusing electrophoresis and how does it work?

separates proteins by pH using their charge

• The gel has a gradient of different pHs.

• Proteins initially move up/down gel based on charge, but stop when they reach their Ip because their charge is 0.

List 4 common polar solvents and 4 non polar solvents used in chromatography?

Polar:

• water

• DMSO

• DMF

• acetone

Nonpolar

• benzenes

• diethyl ethers

• alkanes

• toluene

What is the difference between polar protic solvents and polar aprotic solvents? Give examples of each.

• Polar protic solvents: CAN form H bonds and have a hydrogen atom attached to an electronegative atom (O or N, NOT HF)

  • water

  • alcohols (methanol, ethanol)

  • acetic (ethanoic) acid

  • ammonia (NH3)

  • tBuOH

• Polar aprotic solvents: canNOT form hydrogen bonds and do not have an acidic hydrogen

  • acetone

  • DMSO (dimethyl sulfoxide)

  • DMF (N,N-Dimethyl Formamide)

what is the difference between Ksp and Kf in solutions?

Ksp: eq constant for solubility of OG compound in soln.

Kf: eq constant for formation of complex ions in soln

• measures stability of a complex ion formed b/w metal ions and ligands

What are the 3 types of aqueous solns? describe and give examples of each.

1. Strong electrolyte: ionize completely in H20, allow high electrical conductivity. Ex: Strong acids/bases, salts

2. Weak electrolyte: partially dissociate into ions, weaker electric conductivity. ex: weak acids (acetic), weak bases

3. Non-electrolyte: do NOT dissolve into ions at all, do NOT conduct electricity. ex: sugars, alcohols

Higher ionization energy usually corresponds with higher EN, except for which 3 elements?

He, N, Ar

What type of orbitals of the central atom are involved in bonding in tetrahedral compounds? (think of how many bonds)

sp3, 4 bonds

What type of orbitals of the central atom are involved in bonding in trigonal bipyramidal compounds? (think of how many bonds)

sp3d, 5 bonds

What type of orbitals of the central atom are involved in bonding in octahedral compounds? (think of how many bonds)

sp3d2, 6 bonds

How many orbitals in the s subshell?

1 orbital

how many orbitals in a p subshell?

3 (x,y,z directions)

How many orbitals in a d orbital?

5

how many orbitals in an f shell?

7