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B MCAT > B MCAT- Chem > Flashcards

B MCAT- Chem Flashcards

1
Q

3 elements that can form H-bonds

A

Oxygen
Nitrogen
Fluorine
(Chlorine)

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2
Q

protecting a carbonyl

A

Use a vicinal diol (OH-C-C-OH) forms an acetal to protect a carbonyl (aldehyde, keytone). Acidic conditions will reform the carbonyl.

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3
Q

Mesylates and tosylates

A

Sulfur in the mesylate or tosylate (aromatic ring attached) bond with the oxygen of an alcohol to turn an alcohol into a good leaving group.

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4
Q

protecting an alcohol

A

Acetic anhydride or tosyl chloride can be used to protect an alcohol.

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5
Q

amine vs. imine vs. amide

A

An amine is carbon with a single bond to oxygen.

An imine is a carbon with a double bond to oxygen.

An amide is a carbonyl C bound to a N as well.

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6
Q

strong oxidizing agents

A

Strong oxidizing agents can take a primary alcohol and oxidize it fully to a carboxylic acid. All oxidizing agents can take a secondary alcohol to a keytone.

KMnO4 + heat
Jones reagent
Na2Cr2O7
H2CrO4

Look for oxygen-rich species with metal.

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7
Q

weak reducing agents

A

Sodium borohydride NaBH4

Weak reducing agents do one step of reduction, vs. fully reducing.

Won’t react with an ester.

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8
Q

Weak oxidizing agents

A

primary alcohol to an aldehyde
secondary alcohol to a keytone

Beware to take aromaticity into consideration though–the more stable molecule could require a strong oxidizing agent to make a change.

PCC

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9
Q

Strong reducing agents

A

LiAlH4

carboxylic acid &raquo_space;primary alcohol
keytones&raquo_space; secondary alcohols
esters&raquo_space; alcohols
amides&raquo_space; amines

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10
Q

Reducing agents common in breaking disulfide bonds in a lab

A

beta-mercaptoethanol
dithiothreitol (DTT)

It takes a reducing agent to break a disulfide bond. Requires two S-H bonds to form an S-S bond.

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11
Q

Two main classes of sugars, divided by their functional groups

A

ALDOSES–priority functional group is an aldehyde
KETOSES–priority functional group is a keytone.

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12
Q

hemiacetal
vs.
hemiketal

A

Both have an anomeric C attached to an ether, an alcohol, and a C.

In a hemiacetal, the fourth bond on the anomeric carbon is to a hydrogen.

In a hemiketal, the fourth bond on the anomeric carbon is to another carbon.

Acetal/Ketal has another ester (-OR group) in place of the alcohol.

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13
Q

mutarotation

A

opening and closing of sugar rings in aqueous solution.

Allows the anomeric carbon to rotate between the alpha and beta anomers.

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14
Q

Tollen’s reagent

A

Tollen’s reagent ONLY oxidizes aldehydes to acids. Can therefore be used to aldehydes and keytones and to identify reducing sugars.

(positive test makes silver mirror)

Benedict’s test also tests for reducing sugars.

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15
Q

Fehling’s Solution

A

?????
REDOX test specifically for sugars

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16
Q

pKa + pKb =

A

pKa + pKb = 14 (pKw)

pH + pO=H = 14

[OH][H+]=10^-14

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17
Q

Disassociation constant, ionization constant, equilibrium constant

A

All mean the same thing.

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18
Q

What makes an acid or base strong?

A

Complete disassociation in aqueous solution.

Strong acid Ka>1
Strong base Kb>1

Ka * Kb = Kw (10^-14)

Inert = less reactive than water. Negligible, too small to matter. The conj a/b of strong a/b is inert.

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19
Q

common strong acids

A

HCl
HBr
HI
H2SO4
HNO3
HClO3
HClO4

(note that acidic acid is a WEAK acid)

20
Q

common strong bases

A

NaOH
KOH
Other hydroxides of group 1 metals

21
Q

pKa of water

A

15.7

pKa lower than that = more acidic.
pKa higher than that = more basic.
(pKa of hydronium is -1.7)

22
Q

Hund’s Rule

A

subshells fill with electrons of parallel spins first.

23
Q

Aufbau Principle

A

Electrons fill lower to higher energy subshells.

24
Q

Pauli Exclusion Principle

A

No 2 electrons can have the same four quantum numbers.

25
Q

IR Spec peaks to know…
3100-3500 broad=
3100-3500 multiple sharp=
1700-1750 sharp=

A

3100-3500 broad stretch= -OH
3100-3500 multiple sharp peaks = -NH
1700-1750 sharp peak = C=O carbonyl

26
Q

H NMR Basics

A

Aromatic hydrogens 6-8 ppm.
Aldehydes 8-10 ppm.
Carboxylic acids 10.5-12 ppm.
Most everything else should be in 0-6 ppm range.

Used for MRI.

27
Q

titration formula

A

NA x VA = NB x VB
M acid x vol acid = M base x vol base

28
Q

How does running a fever affect your blood pH?

A

hypothermia is associated with increased pH and hyperthermia with decreased pH.

fever=more acidic blood
cold body temp=more basic blood

29
Q

In simplest terms, Ka=

A

[A-][H+]/[HA]

concentration of ionized H and conjugate base divided by the concentration of acid.

Strong acid will have a Ka ratio greater than 1.

30
Q

electrolyte

A

A substance that carries a charge (is an ion) in water or at biological pH.

31
Q

adipose tissue

A

fat, connective tissue

32
Q

When to use ionic radius to measure distance

A

The distance between two adjacent nuclei is equal to the sum of their ionic radii.

For example, to measure the distance between two adjacent nuclei in an NaCl lattice structure, take the ionic radius of NA + ionic radius of CL = distance between.

33
Q

Arrhenius base

A

an arrhenius base increases the concentration of -OH in solution.

34
Q

Quantum Numbers

A

Principle quantum number = n (shell 1, 2, 3, etc.)

Angular momentum quantum number = l (indicates shape of region, l=n-1, 0=s, 1=p, etc.)

magnetic quantum number = m (sub)l (indicates orientation of the orbital; can be an value -l to +l; if l=0, ml=0, s spherical orbital with only one orientation; if l=1, ml=-1, 0, or +1 p orbital with 2 possible orientations

spin quantum number = m(sub)s (spin up or spin down, +1/2 or - 1/2)

35
Q

rigidity of double bonds depends on…

A

rigidity of double bonds depends on the pi electrons’ ability to delocalize; more resonance structures indicates less rigidity.

36
Q

frequency factor refers to…

A

frequency factor refers to the frequency of collisions of molecules.

37
Q

Thin Layer Chromatography (TLC)

A

very similar to the kitchen color experiment.

Stationary phase is a polar silica gel (Si and O).

Mobile phase is a nonpolar solution.

Based on solubility, nonpolar molecules migrate the most; polar molecules migrate less.

Retention factor Rf value: Ratio of movement over the solvent front (control). Rf value closer to 1 = more mobile.

38
Q

Column Chromatography

A

Goal is to separate a protein. Stationary phase is beads with additive. Wash and elute. Rather than measuring distance as in gel or paper chromatography techniques, let solution flow (elute) into beakers and measure time that it takes to get through.

Can use spectroscopy or gel electrophoresis to analyze the resulting solutions further.

39
Q

Gel filtration column chromatography

A

=size exclusion.

Beads are porous, and smaller molecules get stuck interacting and take longer to get through.

Large molecules move through column much more quickly and will be first fractions to come out. Later fractions will be smaller molecules.

40
Q

Ion exchange chromatography

A

1) Anion exchange–column (stationary phase) is positively charged, so anions stick.

2) Cation exchange–column is negatively charged, so cations stick.

Must choose a binding buffer based on the isoelectric point (pI) of the protein of interest. i.e. If you want the protein positively charged for cation exchange, choose a buffer with a pH less than the pI of the protein.

41
Q

fractional distillation

A

Separates two liquids with different boiling points.

42
Q

IR Spec peaks:
hydroxyl C-O
carbonyl C=O
amino N-H

A

hydroxyl C-O, broad at 3300
carbonyl C=O, at 1750
amino N-H, sharp at 3300

43
Q

Ionization energy

A

The energy required to remove an electron from an atom in the gaseous state, creating a positive charge.

44
Q

electron affinity

A

The amount of energy a neutral atom releases when it gains an electron and becomes negatively charged.

45
Q

Work function

A

The work function is a measure of energy to release an electron from the surface of a metal, creating a positive charge.

B MCAT (11 decks)

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