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z MCAT: Areas Of Opportunity > Organic > Flashcards

Organic Flashcards

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1
Q

With infrared spectroscopy, one absolutely needs to know three characteristic absorptions. One of those is alcohol, which has a __________ peak and absorbances at _________

A

Broad; 3300 cm -1

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2
Q

With infrared spectroscopy, one absolutely needs to know three characteristic absorptions. One of those is carboxyl in acid -OH group, which has a __________ peak and absorbances at _________

A

Broad; 3000 cm-1

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3
Q

With infrared spectroscopy, one absolutely needs to know three characteristic absorptions. One of those is a carbonyl group, which has a __________ peak and absorbances at _________

A

Sharp (deep); 1700 cm-1

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4
Q

With infrared spectroscopy, one absolutely needs to know three characteristic absorptions. One of those is N-H bond, which has a __________ peak and absorbances at _________

A

Sharp peak at 3300cm-1

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5
Q

When it comes to NMR on test day, counting the number of peaks and unique hydrogens may be enough but there are shifts to consider such as for alkyl groups: ________ppm

A

0 to 3

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6
Q

When it comes to NMR on test day, counting the number of peaks and unique hydrogens may be enough but there are shifts to consider such as for alkynes: ________ppm

A

2 to 3

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7
Q

When it comes to NMR on test day, counting the number of peaks and unique hydrogens may be enough but there are shifts to consider such as for alkenes: ________ppm

A

4.6 to 6

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8
Q

When it comes to NMR on test day, counting the number of peaks and unique hydrogens may be enough but there are shifts to consider such as for aromatics: ________ppm

A

6 to 8.5

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9
Q

When it comes to NMR on test day, counting the number of peaks and unique hydrogens may be enough but there are shifts to consider such as for Aldehydes: ________ppm

A

9 to 10

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10
Q

When it comes to NMR on test day, counting the number of peaks and unique hydrogens may be enough but there are shifts to consider such as for carboxylic acid: ________ppm

A

10.5 to 12

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11
Q

For NMR spectroscopy, what effect does electronegative groups have on the protons.

A

They pull electron density away from the protons causing it to be more deshielded and will result in the proton being further downfield

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12
Q

IR spectroscopy is most useful for distinguishing:
A) double and triple bonds
B) C-H bonds
C) Chirality of molecules ‘
D) relative percentage of enantiomers in mixtures

A

A) double bonds and triple bonds

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13
Q 
Before absorbing an UV photon, electrons can be found in
A) the HOMO only
B) the LUMO only
C) both the HOMO and the LUMO
D) neither the HOMO nor the LUMO
A

A) the HOMO only

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14
Q

Wave number is directly proportional to _______

A

Frequency

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15
Q

In an IR spectrum, extended conjugated double bonds affects the absorbance band of carbonyl stretches compared with a normal absorption by how?

A

The absorbance band will occur at a lower wave number

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16
Q

What are the three intermolecular forces that affect solubility?

A

H bonds

Dipole-dipole interactions

Van der Waals (London) forces:

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17
Q

What are some examples of compounds that can do H bonding? And what will they move most easily into?

A

Alcohols or acids

Move most easily into the aqueous layer

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18
Q

List in order the forces that affect solubility that move most easily into the aqueous layer to least likely to move into the aqueous layer

A

Most likely: H bonding

                Dipole-dipole

Least likely:Van der Waals

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19
Q

The water layer is called the ______. The nonpolar ether layer is called the ________

A

Aqueous phase (layer)

Organic phase (layer)

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20
Q

What piece of equipment is used in extractions?

A

Separatory funnel

It is more common for the organic layer to be on top but the denser layer will always be on the bottom

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21
Q

What is the “wash process”?

A

Small amount of solute is used to extract and remove impurities

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22
Q

What does filtration do?

A

Isolates a solid (residue) from a liquid (filtrate)

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23
Q

What is recrystalization

A

A method for purifying crystals in solution

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24
Q

What is the best way to separate two liquids with similar boiling points (less than 25 degrees Celsius apart)?

A

Fractional distillation

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25
Q

What method do you use when you want to distill a liquid with a boiling point over 150 degrees Celsius?

A

Vacuum distillation

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26
Q

What technique should only be used to separate liquids that boil below 150 degrees Celsius and have at least a 25 degree Celsius difference in boiling points

A

Simple distillation

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27
Q

How does chromatography separate compounds?

A

Based on how strongly they adhere to the solid, or stationary phase

*** how easily they come off into the mobile phase

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28
Q

What does thin layer chromatography (TLC) use for a stationary phase?

A

Silica gel, a highly polar substance

***any polar compound will adhere to the gel well and those move through (elute) slowly

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29
Q

What is the medium used for stationary phase for paper chromatography?

A

Cellulose

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30
Q

What is used as the mobile phase in TLC?

A

An organic solvent of weak to moderate polarity so it doesn’t bind well to the gel.

Nonpolar compounds dissolve in the organic solvent and move quickly as the solvent moves up the plate, where as the more polar molecules stick to the gel,

Thus the more nonpolar the sample, the farther up the plate it’ll go

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31
Q

Explain the reverse phase chromatography technique with the stationary phase

A

The stationary phase is nonpolar so polar molecules move up the plate quickly while nonpolar molecules stick more tightly to the stationary phase.

*** the exact opposite of TLC

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32
Q

When TLC is performed, how are compounds generally identified?

A

Using the retardation factor (Rf)

Which is the distance spot moved divided by the distance solvent front moved

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33
Q

What are the principles behind column chromatography?

A

1) uses an entire column filled with silica or aluminum beads as an absorbent (allows for better separation)
2) uses gravity to move the solvent and compounds down the column
3) the more similar the sample is to the mobile phase, the faster it elutes it and vice versa

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34
Q

What technique can be used to separate and collect macromolecules such as proteins or nucleic acids?

A

Column chromatography

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35
Q

What type of chromatography are the beads in the column coated with charged substances so that they attract or bind compounds that have an opposite charge?

A

Ion-exchange chromatography

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36
Q

What is the mechanism of ion exchange chromatography ?

A

The beads in the column are coated with charges so when something comes through the column it’ll bind to those oppositely charged beads. Then to release the bound DNA or proteins use a salt gradient to elute the charged molecules that have stuck to the column

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37
Q

What type of chromatography has beads in the column that contain tiny pores of varying sizes that allows small compounds to enter the beads and the larger molecules to travel through the column faster?

A

Size-exclusion chromatography

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38
Q

What is a common approach to protein purification?

A

Use an ion exchange column followed by a size-exclusion column

39
Q

When would one use affinity chromatography? Similar to his-tagging of proteins

A

When you want to bind a protein of interest to the column that has high affinity for that protein

Stationary phase commonly used for this is Nickel which is commonly used in mechanisms like his-tagging proteins

40
Q

What are characteristics of volatile compounds

A

They have low melting point, sublimate solids or vaporizable liquids

41
Q

What is the mechanism of gas chromatography?

A

The volatile sample is injected into the column and moves with the gaseous mobile phase through a stationary liquid or solid phase; a computer identifies the components

42
Q

What does mass spectroscopy involve?

A

The ionization and fragmentation of compounds

These fragments are then run through a magnetic field, which separates them by their mass to charge ratio

The total molecular weight can thus be determined

43
Q

What is the HPLC elutent? And what is the mechanism of HPLC?

A

Elutent is a liquid

A small sample is injected into the column and separation occurs as it flows through

The compounds pass through a detector and are collected as the solvent flows out of the end of the apparatus.

44
Q

What are the similarities and differences in HPLC and gas chromatography

A

Similarities: the entire system is computerized

Differences: uses liquid pressure instead of gas

45
Q

What are structural isomers

A

Share the same molecular formula but have different structures

46
Q

What re examples of physical properties and what are physical properties?

A

No change in composition of matter

Ex: melting point, boiling point, solubility, odor, color, density

47
Q

What are conformational isomers? And how are they best visualized?

A

Differ in formation around single (sigma bonds)

Arise from the fact that varying degrees of rotation around single bonds can create different levels of strain

Newman projection

48
Q

What are the Newman projection names in order from lowest energy level (most stable) to highest energy level (least stable)

A

Lowest energy level: staggered conformation (anti conformation, two largest groups are farthest away from each other)

–eclipsed: two largest groups are 120 degrees apart

  • gauche: two largest groups are 60 degrees apart
  • totally eclipsed: two largest groups are on top of each other (0 degrees apart) Highest energy (least stable)
49
Q

What makes an object chiral?

A

If this mirror image cannot be superimposed on the original object (there is a lack of an internal plane of symmetry

50
Q

What are enantiomers?

A

Non superimposable mirror images that have the same connectivity but opposite configurations at every chiral center in the molecule

Have identical physical and chemical properties except they have different optical activity and reactions in chiral environments

51
Q

What are diastereomers?

A

Non-mirror-image configurational isomers

Occur when a molecule has two or more stereogenic centers and differs at some but not all of these centers

Diastereomers are required to have multiple chiral centers. So for an molecule with “n” chiral centers, there are 2^n possible stereoisomers

52
Q

Stereoisomers that are mirror images of each other are __________. Stereoisomers that are not mirror images of each other are _____________.

A

Enantiomers

Diastereomers

53
Q

Diastereomers have what properties?

A

Have different chemical properties but may behave similarly in some reactions because they have the same functional groups

They are arranged differently in space so will consistently have different physical properties.

Cannot rotate plane polarized light

54
Q

What is the definition of cis-trans isomers?

A

A specific subtype of diastereomers in which substituents differ in their position around an immovable bond such as a double bonds or a cyclic ring structure

55
Q

What are Meso compounds?

A

Molecules that have chiral centers and have an internal plane of symmetry

56
Q

What two things must a molecule have in order to have optical activity?

A

Must have chiral centers within it and must also LACK a plane of symmetry.

If there is an internal plane of symmetry, then the molecule is not optically active

57
Q

What does configuration mean and what are the definition of the two types of configurations, relative and absolute?

A

Configuration of a stereoisomer refers to the spatial arrangement of the atoms or groups in the molecule

Relative configuration of a chiral molecule is its configuration in relation to another (often through chemical inversion)

Absolute configuration: of a chiral molecule describes the exact spatial arrangement of these atoms or groups, independent of other molecules

58
Q

When is E and Z nomeclature used? And how is priority set?

A

Used for compound with polysubstituted double bonds

Priority based on the highest atomic number

If the two highest priority substieutents on each carbon are on the same side of the double bond then that is termed Z

If they are on opposite sides then it is termed E

59
Q

What are the steps in determining R and S forms?

A

1) assign priority based on highest atomic number
2) invert the stereochemistry by moving the lowest priority to the back of the molecule. *** but with that remember to switch the final configuration to the opposite to compensate

3) Draw a circle connecting from 1 to 2 to 3 of the priorities. If the circle is clockwise it is called R. If the circle is counterclockwise it is called S

60
Q

What do R and S help determine?

A

The absolute configuration at a chiral center

61
Q

When will an acid base reaction proceed?

A

If the products that will be formed (conjugate acid and conjugate base) are weaker than the original reactants

62
Q

When do coordinate covalent bonds occur?

A

When Lewis acids and bases interact

63
Q

Water acts as a base in a(n) _________ solution

Water acts as a acid in a(n) ________ solution

A

Acidic solution

Basic solution

64
Q

What range are the pKa s for acids, bases, weak organic acids?

A

Acidic molecules will have a smaller (or even negative) pKa

Mor basic molecules will have a larger pKa

Acids with pKa ‘s below -2 are considered strong acids an completely dissociate in aqueous solutions

Weak organic acids often have pKa values between -2 and 20

65
Q

Bond strength relationship to acidity?

What is electronegativity relationship to acidity?

A

Bond strength decreases down the periodic table, acidity therefore increases

The more electronegative an atom, the higher the acidity

*** when these two trends oppose each other, low bond strength takes place

66
Q

What functional groups act as acids?

A

Alcohols

Aldehydes and ketones at the alpha carbon (carbon adjacent to the carbonyl)

Carboxylic acids and most carboxylic acid derivatives

** these are easy to target with a basic (or nucleophilic) reactants bc they readily accept a lone pair

67
Q

What functional groups act as bases?

A

Amines and amides

*** Amines are capable of forming coordinate covalent bonds by donating a lone pair to a Lewis acid

68
Q

Good nucleophiles tend to be good _______

A

Base

69
Q

What do nucleophiles tend to have? And what key elements should you keep an eye out for on test day that are key in identifying them.

A

Lone pairs or pi bonds that CN be used to form covalent bonds to electrophile

** Look for Carbon, Hydrogen, Oxygen, or Nitrogen on test day

70
Q

How is nucleophilicity affected by:

Charge?

Electronegativity?

Steric Hindrance?

Solvent?

A

Charge: nucleophilicity increases with increasing electron density

EN: nucleophilicity decreases as EN increases

Steric Hindrance: bulkier molecules are less nucleophilic

Solvent: Protic solvents hinder nucleophilicity by protesting nucleophile or through H bonding

71
Q

What are aprotic solvents? And what are some examples?

A

Aprotic solvents cannot hydrogen bond

DMF, DMSO, acetone

72
Q

What are common examples of protein solvents? And what are protein solvents?

A

Protect solvents can H bond

Examples: carboxylic acids, ammonia/ amines, water/ alcohols

73
Q

In polar protic solvents, what is the nucleophilicity of the halogens in from most to least

A

I-,Br-,Cl-, F-

74
Q

In polar aprotic solvents, what is the nucleophilicity of the halogens from most to least

A

F-, Cl-, Br-, I-

75
Q

What is an electrophile and what is an example of a really good one?

A

Electrophiles will almost always act as Lewis acids in reactions

A greater degree of positive charge increases electrophilicty

76
Q

How are electrophilicity and acidity related?

A

Essentially identical when it comes to reactivity.

Just as alcohols, aldehydes and ketones, carboxylic acids and their derivatives act as acids, they also act as electrophiles and can make good targets for nucleophilic attack

77
Q

The more substituted a carbon is the more likely _______ reaction will happen

The less substitieuted the carbon is the more reactive it is in ________ reactions

SN1 and SN2 reaction comparison

A

SN1

SN2

78
Q

What does O3, then Zn form when reacted with and Alkene?

A

Aldehyde and a ketone

79
Q

What results when an alkene is reacted with O3 then H2O2?

A

Carboxylic acid and a ketone

80
Q

What results when you react an alkene with OsO4 or KMnO4,OH-?

A

Vicinity idol formation

81
Q

Alcohols are readily oxidized to carboxylic acids by any oxidizing agent other than ________, which will only oxidize primary alcoholic to _________.

A

PCC

Aldehydes

82
Q

What are mesylates and how are they prepared?

A

A compounds containing the functional group -SO3CH3

They are prepared using methylsufonyl chloride and an alcohol in the presence of a base

83
Q

what are two subgroups of stereoisomers?

A

conformational

configurational

84
Q

what are conformational stereoisomers?

A

simple rotation of a sigma bond
no bond breaking
same connectivity
same substituents

85
Q

what are configurational stereoisomers?

A

bond breaking required
same connectivity
same substituents

86
Q

what are constitutional isomers?

A

different elements
bond breaking necessary
connectivity is different
different names

87
Q

configurational isomers have two branches. what are those two branches?

A

optical isomers

cis/trans isomers

88
Q

if there are no cis/trans isomers and they are configurational isomers then they are ______

A

optical isomers

89
Q

what are the two branches of optical isomers?

A

enantiomers

diastereomers

90
Q

how do enantiomers differ?

A

1) rotation of plane polarized light

2) behavior in chiral environments

91
Q

what are enantiomers?

A

configurational isomers that are nonsuperimposabe mirror images of eachother. contain chiral center(s)

92
Q

what are diastereomers?

A

configurational isomers with MORE THAN one stereocenter that are nonsuperimposable and NOT mirror images

93
Q

what are the possible subtypes of configurational isomers?

A

cis-trans isomers

optical isomers: enantiomers and diastereomers

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