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MCAT gen chem > Intro to ochem > Flashcards

Intro to ochem Flashcards

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1
Q

sigma bonds

A

forms when the bonding pair of electrons are localized to the space directly between the two bonding atoms. it is the lowest energy strongest and most stable type of covalent bond

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2
Q

a pi orbital

A

is created by overlapping p orbitals

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3
Q

sigma bonds are formed

A

in the area where hybrid orbitals of two atoms overlap

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4
Q

pi bonds are formed

A

by the overlap of pure p orbitals

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5
Q

number of hybrid orbitals must equal the

A

number of sigma bonds plus the lone pairs

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6
Q

valence shell electron pair repulsion

A

states that electrons in an orbital seek to minimize their energy by moving as far away from other electron pairs as possible, minimizing the repulsive forces between them

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7
Q

sp angle

A

180

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8
Q

sp2 angle

A

120

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9
Q

sp3

A

109.5

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10
Q

sp3d

A

90,120

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11
Q

sp3d2

A

90,90

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12
Q

delocalized electrons

A

sometimes bonding electrons are spread out over three or more atoms

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13
Q

aromaticity

A

is the increased stability of a cyclic molecule due to electron delocalization. must follow huckel’s rule 4n+2 will be aromatic

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14
Q

nucleophiles are also called

A

lewis bases, with a partial negative charge seeking positively charged nuclei

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15
Q

electrophilic functional groups

A

have a partial positive charge and seek electrons

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16
Q

structural isomer

A

have the same molecular formula but different bond-to-bond connectivity

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17
Q

conformational isomers

A

are not true isomers. they are different spatial orientations of the same molecule

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18
Q

highest energy conformation and lowest

A

eclipsed and staggered

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19
Q

stereoisomers

A

two unique molecules with the same molecular formula and the same bond-to-bond connectivity

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20
Q

enantiomers

A

are non-superimposable mirror images of one another. they have the same molecular formula and connectivity but are not the same molecule because they differ in their configuration. they must have opposite absolute configuration at each and every chiral carbon. have the same chemical properties

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21
Q

chirality

A

a carbon is chiral when it is bonded to four different substituents

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22
Q

relative configuration

A

is not related to absolute configuration but two molecules have the same relative configuration about a chiral carbon if they differ by only one substituent and the other substituents are oriented identically about the carbon

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23
Q

to find how a configuration rotates light you have to find it

A

experimentally

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24
Q

if the compound rotates plane polarized light clockwise

A

it is designated with + for dextrorotary

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25
Q

if the compound rotates plane polarized light counterclockwise

A
  • levoratory
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26
Q

diastereomers

A

have the same molecular formula and same bond-to-bond connectivity but are not mirror images of each other and are not the same compound

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27
Q

diastereomers have

A

the same absolute configuration at one or more of their chiral centers.

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28
Q

how do diastereomers differ from each other

A

they differ in their physical properties rotation of plane-polarized light, melting points, boiling points, solubilities and their chemical properties

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29
Q

meso compound

A

has multiple chiral centers but is optically inactive they have a plane of symmetry through their center which divides into two halves that are mirror images of each other. considered achiral

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30
Q

epimers

A

are diastereomers that differ in configuraton at only one chiral carbon

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31
Q

anomers

A

are cyclic diastereomers that are formed when a ring closure occurs at an epimeric carbon.

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32
Q

cis/trans isomers

A

geometric isomers that have substituents on the same side (cis) or on a different side (trans)

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33
Q

cis molecules have

A

higher boiling points due to their substituents and lower melting point. they also have a dipole moment

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34
Q

stronger bases are strong

A

nucleophiles

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35
Q

alcohols boiling point property

A

higher molecular weight is a higher boiling point and goes down with branching

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36
Q

strongly electron donating groups

A

oxygen, alcohol, amine

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37
Q

moderately donating

A

-OR

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38
Q

weakly donating

A

-R

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39
Q

strong electron withdrawing groups

A

O-N=O R-N-R+ Cl-C-Cl

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40
Q

moderatly withdrawying

A

carbonyls, aledhydes, ketones, esters, carboxyilic acids, tosylates, cyanide

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41
Q

acid trend based on how strong

A

methyl>primary > secondary> tertiary

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42
Q

hydrocarbons do what

A

donate electrons

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43
Q

carbonyl groups do what

A

electron withdrawing

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44
Q

tosylates and mesylates are used as

A

protection of alcohols. the conversion to a sulfonate prevents the alcohol from acting as an acid or undergoing other reactions

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45
Q

ethers are very good

A

solvents, even better than alcohols

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46
Q

two important characteristics of carbonyls

A
  1. planar stereochemistry

2. polarity: partial negative charge on oxygen partial positive charge on carbon

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47
Q

how are peptide bonds formed

A

the amino acid attacks the carbonyl carbon of the carboxylic acid on another amino acid creating an amide

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48
Q

least reactive and strongest carboxylic acid derivative

A

amides

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49
Q

aldehydes and ketones undergo what sort of nucleophilic reaction

A

addition due to not having a good leaving group

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50
Q

ketones and aldehydes exist as what at room temperature

A

as keto-enol tautomers in which there is a shift from a carbonyl to an alkene with an alcohol.

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51
Q

aldehydes and ketones react with alcohols forming

A

hemiacetals and hemiketals

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52
Q

hemiacetals and hemiketals reacted with alcohol results in

A

acetal and ketals

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53
Q

sucrose

A

1’1 glycosidic linkage: glucose and fructose or 1’2

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54
Q

maltose

A

alpha 1,4’ glycosidic linkage two glucose molecules

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55
Q

lactose

A

beta 1’4 galactosidic linkage: galactose and glucose

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56
Q

cellulose

A

beta 1’4 glycosidic linkage a chain of glucose molecules

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57
Q

amylose (starch)

A

alpha 1’4 glycosidic linkage a chain of glucose molecules

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58
Q

amylopectin

A

alpha 1’4 glycosidic linkage a branched chain of glucose molecules with alpha 1’6 glucosidic linkages forming the branches

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59
Q

glycogen

A

alpha 1’4 glycosidic linkage: a branched chain of glucose molecules with alpha 1,6 glucosidic linkages forming the branches

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60
Q

extensive properties

A

are proportional to the size of the system

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61
Q

intensive properties

A

are independent of the size of the system

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62
Q

volume and moles are examples of

A

extensive properties

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63
Q

pressure and volume are examples of

A

intensive properties

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64
Q

the greater the translational kinetic energy of gas molecules

A

the higher the temp

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65
Q

dividing one extensive property by another gives

A

an intensive property

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66
Q

absolute zero

A

-273.15 degrees celsius

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67
Q

an increase in 1 degree celsius is equivalent to

A

one degree of kelvin increase

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68
Q

to go from celsius to kelvin

A

add 273

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69
Q

difference between kelvin and celsius

A

celsius is a relative scale while kelvin actually measures the thermal energy

70
Q

open systems

A

can exchange both energy and mass

71
Q

closed systems

A

mass cannot be exchanged but energy can be

72
Q

isolated systems

A

energy and mass cannot be exchanged

73
Q

state functions

A

is the physical condition of a system as described by a specific set of thermodynamic properties

74
Q

examples of state functions

A

internal energy (U), temperature (T), Pressure (P), Volume (V), Enthalpy (H), entropy (S), Gibbs energy (G)

75
Q

pathway functions

A

depend on the pathway used to achieve that state

76
Q

examples of pathway functions

A

work and heat

77
Q

thermal energy is energy on what level

A

macroscopic level

78
Q

internal energy is energy on what level

A

microscopic level

79
Q

internal energy includes

A

vibrational energy, rotational energy, translational energy, electronic energy, intermolecular potential energy, and rest mass energy

80
Q

vibrational energy

A

is created by the vibration of atoms within a molecule. vibrational energy makes an insignificant contribution to internal energy. gas has no vibrational energy

81
Q

rotational energy

A

is created by the rotation of a molecule around its center of mass

82
Q

translational energy

A

is created by movement of the center of mass of a molecule

83
Q

electronic energy

A

is the potential electrical energy created by the attractions between electrons and their nuclei. in a chemical reaction changing electronic energy accounts for the greatest change in internal energy

84
Q

intermolecular potential energy

A

is created by intermolecular forces between molecular dipoles

85
Q

rest mass energy

A

is the energy described by einstein’s E=mc^2. the sum of these energies for a very large group of molecules is the internal energy.

86
Q

internal energy of an ideal gas has to depends on

A

temperature

87
Q

only two ways to transfer energy between systems

A

heat and work

88
Q

zeroth law of thermodynamics

A

states that two systems in thermal equilibrium with a third system are in thermal equilibrium with each other

89
Q

conduction

A

is thermal energy transfer via molecular collisions. it requires direct physical contact

90
Q

an objects ability to conduct heat is called its

A

thermal conductivity (k)

91
Q

convection

A

is thermal energy transfer via fluid movements. differences in pressure or density drive warm fluid in the direction of cooler fluid.ex ocean and air currents

92
Q

radiation

A

is thermal energy transfer via electromagnetic waves

93
Q

blackbody radiators

A

have an emissivity of 1 and absorb 100% of radiation energy

94
Q

work done by the system is considered

A

negative

95
Q

first law of thermodynamics

A

energy is conserved

96
Q

energy is transferred out of the system in

A

in expansion delta E is negative

97
Q

enthalpy equation

A

H=U (internal energy) +PV

98
Q

enthalpy equation under constant pressure conditions

A

change in internal energy + P delta V

99
Q

formation of bonds always requires what? and the breaking of bonds always results in?

A

energy, releasing energy

100
Q

positive enthalpy change

A

endothermic

101
Q

negative enthalpy change

A

exothermic

102
Q

anabolic reactions are usually

A

endothermic

103
Q

catabolic reactions are usually

A

exothermic

104
Q

entropy change of the universe equals

A

change in entropy of the system+ change in entropy of the surroundings= change in entropy of the universe

105
Q

how does temp affect entropy

A

it increases it

106
Q

third law of thermodynamics

A

assigns a zero entropy value to any pure element or compound in its solid form at absolute zero and in internal equilibrium

107
Q

change in entropy equation

A

q(heat)/ T

108
Q

reactions under non-standard states free energy equation

A

delta g= delta g knot+ RTlnq

109
Q

reactions at equilibrium gibbs free energy equation

A

delta g= -RTlnk

110
Q

entropy units

A

J/K

111
Q

if volume decreases in a given reaction then shift to

A

one with less gas molecules

112
Q

relationship between atmospheres, mmhg and torr

A

1atm=760mmhg=760torr

113
Q

internal energy equation

A

change in internal energy= heat transfer+ the work for a given physical process (E= Q+W)

114
Q

adiabatic process internal energy equation

A

E=w

115
Q

isothermal process internal energy equation

A

E=0 0=Q+W

116
Q

isovolumetric process internal energy equation

A

w=0 E=q

117
Q

STP

A

1 atm 273K and 22.4 liters

118
Q

real gases behave most ideally when

A

temperature is high and volume is large

119
Q

ideal gas

A

gas molecules have no size. zero molecular volume
gas molecules do not exert forces on one another
gas molecules have completely elastic collisions
the average kinetic energy of gas molecules is directly proportional to the temp of the gas

120
Q

partial pressure

A

is the total pressure of the gaseous mixture multiplied by the mole fraction of the particular gas

121
Q

real gases deviate from ideal gases when

A

high pressures and low temp

122
Q

how real gases differ from ideal gases in pressure and volumer

A

Vreal>Videal

Preal

123
Q

specific heat units

A

J/kgK or cal/gC(degree celsius)

124
Q

amount of energy required to raise one gram of water by one degree Celsius

A

1 Cal=1000cal=4184 J

125
Q

coffee cup calorimeter

A

keeps the pressure constant therefore it measures heats of reactions

126
Q

bomb calorimeter

A

a bomb calorimeter measures internal energy change in a reaction by keeping constant volume.

127
Q

there is a negative slope on the phase diagram for water because

A

waters solid phase is less dense than its liquid phase

128
Q

critical temperature is

A

the temperature above which the substance cannot be liquified regardless of how much pressure is applied

129
Q

equivalents in an acid base reaction

A

is defined as the mass of acid or base that can donate or accept one mole of protons. ex: 1 molar solution of H2SO4 is called a 2 normal solution because it can donate 2 protons from each H2SO4

130
Q

normality

A

equivalents/ Liter of solution

131
Q

in solutions if the overall reaction releases heat then the new intermolecular bonds are

A

stronger than the intermolecular attractions within the pure substances

132
Q

negative heat of solution

A

indicates the formation of stronger intermolecular bonds

133
Q

positive heat of solution

A

indicates the formation of weaker intermolecular bonds

134
Q

dissolution of one substance into another

A

causes an increase in entropy except for a gas into a liquid or solid

135
Q

vapor pressure of the liquid

A

the pressure created by the molecules in the open space at equilibrium

136
Q

when vapor pressure of a liquid is equal to atmospheric pressure

A

the liquid boils

137
Q

the melting point is when the vapor pressure of the solid is equal to

A

the vapor pressure of the liquid phase of that substance

138
Q

nonvolatile solute

A

a solute with no vapor pressure

139
Q

volatile solute

A

a solute with a vapor pressure

140
Q

nonvolatile solutes do what to vapor pressure

A

decrease it

141
Q

volatile solutes do what to vapor pressure

A

increase it

142
Q

for nonvolatile solution

A

use the sum of the partial pressure of pure liquid and the mole fraction of the liquid

143
Q

partial vapor pressure for volatile solutions

A

Pv=XaPa+XbPb

144
Q

solubility product

A

solids are left out of the equation

145
Q

spectator ions

A

are ions not included in the equilibrium expression for solubility

146
Q

nearly all ionic compounds containing nitrate, ammonium, and alkali metals

A

are soluble

147
Q

ionic compounds containing halogens are

A

soluble except for mercury, silver and lead (Hg, Pb, Ag)

148
Q

sulfate compounds are

A

soluble except for mercury, lead, and the heavier alkaline earth metals (Hg, Pb, Ca, Sr, Ba)

149
Q

compounds containing the heavier metals Ca, Sr, Ba

A

are soluble when paired with sulfides and hydroxides

150
Q

carbonates, hydroxides, phosphates, and sulfides

A

CO3, PO4, S, OH are generally insoluble

151
Q

pressure increases the solubility of

A

gases

152
Q

Henry’s law describes the solubility of gases

A

C (solubility of gas a ) = Ka (henry’s constant) Pv (vapor partial pressure of gas a above the solution)

153
Q

gas solubility decreases with

A

an increase in temperature

154
Q

heavier larges gases tend to

A

experience greater van der waals interactions and tend to be more soluble

155
Q

gases that chemically react with the solvent

A

have a greater solubility

156
Q

redox titrations are used for

A

finding the molarity of a reducing agent

157
Q

half equivalence point

A

near the middle of the gradual increase

158
Q

equivalence point

A

where the voltage suddenly shoots up

159
Q

when choosing an indicator what do you look for

A

an indicator that changes color as close as possible to the expected equivalence point

160
Q

electrical potential

A

the more positive the potential the more likely the reaction is to proceed

161
Q

to find the electrical potentials

A

separate the reaction into its two halves and add the half reaction potentials

162
Q

galvanic cell

A

offers an alternative pathway for the flow of electrons through phases. the electric potential generates a current from one phase to another in a conversion of chemical energy to electrical energy

163
Q

where in the galvanic cell does oxidation and reduction occur

A

oxidation at the anode and reduction at the cathode

164
Q

current travels in the opposite direction as

A

electrons

165
Q

the galvanic cell always has positive

A

cell potential

166
Q

electrolytic cell properties

A

have a negative emf and the cathode is negative while the anode is positive. needs an outside energy source to drive the reaction

167
Q

half equivalence point

A

where the concentration of acid equals the concentration of its conjugate base

168
Q

pH is equal to pKa at

A

the half equivalence point

169
Q

PI for acidic or basic amino acids

A

PI is the average of the first two pka values for a basic amino acid and PI is the average of the second and third pka for the acidic amino acid

170
Q

buffers are made from

A

weak acids and its conjugate base

MCAT gen chem (2 decks)

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