Midterm 1 Material Flashcards
0
Q
What is used to describe the schronidger wave functions of atomic orbitals?
A
The principle Quantum number is used to describe the wavefunctions of atomic orbitals
1
Q
What model do we use to describe an atom and its components in this day and age?
A
We use the Bohr Model of the atom, which describes electrons moving in specific orbits (hence the phrase: Orbitals) and we enhance this idea using basic quantum mechanics, specifically the mathematical expression the Schodinger Equation with describes the wave functions of electron orbitals
2
Q
Which electrons are typically involved with bonding interactions between two atoms?
A
The electrons with the highest principle quantum number, or the valence electrons, are the ones typically involved with bonding. Quantum numbers range from 1-4
3
Q
What are Azimuthal Quantum Number?
A
These numbers describe the spatial distribution of the orbital with respect to the nucleus and indicates the angular momentum of the orbital.
The numbers range from m=0,1,2,3….
4
Q
What orbitals are allowed for quantum number 1
A
quantum number 1 are the 1s orbital
5
Q
What is a nodal Plane?
A
Nodal Plane exist in 2p orbitals, it contains the nucleus and it perpendicular to the orbital axis. The electron density is zero at the nucleus.
6
Q
What is the magnetic Quantum Number?
A
The magnetic Quantum number is associated with a third set of quantum numbers
the p orbitals have -1,0,1 and each one represents one of the three different orthogonal directions in space
the d orbitals have the magnetic quantum numbers -2,-1,0,1,2
7
Q
What is the phasing of atomic orbitals
A
the phasing of an atomic orbital is a result of the mathematical functions describing the orbitals. One color indicates the function is positive in this defined region of space while the other color indicates that the function is negative. The probability of finding an electron in the positive or negative region is the same.
8
Q
What is electron density or Electron Distribution?
A
Electron density is the probability of finding an electron within a particular part of the orbital and it is related to the square of the mathematical function that describes the orbital.
9
Q
the fourth and final quantum number is what?
A
The fourth and final quantum number is Ms or magnetic spin number, associated with the spin of an electron. the Ms value can be either +1/2 or -1/2. the numbers of the two values must be oppositely signed if they exist within the same orbital.
10
Q
What is Correlation regarding electrons and orbital theory?
A
Correlation is the ability of an electron to feel the trajectory of another electron and therefore alter its own course so as to minimize coulombic repulsions and keep the energy of the system minimum. This results because of electrons negative charged, particle like character that causes them to repel one another.
11
Q
Electron Configuration of an atom describes all the atomic orbitals that are populated with electrons? How do we write this out
A
1s^2 2s^2 2p^2 … with the superscript designating the number of electrons within the orbitals
12
Q
What is an electron diagram?
A
An electron diagram describes the atomic orbitals by representing them as horizontal lines. the higher the line on the electron diagram, the higher the energy level for the atomic orbital.
13
Q
What is the Aufbau principle?
A
Electrons will occupy the lowest energy level first, only two electrons can be in each orbital, and the two electrons must be spin paired.
14
Q
What is Hunds Rule?
A
Hunds Rule discusses degenerate orbitals. degenerate orbitals are those that have the same energy. Degenerate orbitals will be singly occupied first and their spin states will be the same for all singly occupied orbitals.
15
Q
What is the octet Rule?
A
The octet rule states that atoms are most stable when their valence shell, the one with the highest principle atomic number, is ful
16
Q
What is the valence number and how can you figure out what an atoms valence number will be?
A
The valence number reflects how many bonds an atom can form; the valence number can be derived from an electronic diagram and the octect rule.
17
Q
What is the formal charge?
A
The formal charge is referred to as the overall charge of the atom or molecule, even though the entire atoms charge is delocalized the summation of all the individual charge distributions gives the formal charge.
18
Q
What is the formula for formal charge?
A
The formula for formal charge is
formal charge= # valence electrons - number of unshared electrons - 1/2 the number of shared electrons
19
Q
What does VSEPR stand for?
A
VSEPR stands for valence-shell electron-pair repulsion
20
Q
What is the VSEPR Rule?
A
The VSEPR rule indicates that al group emanating from an atom where single double or triple bonds or lone pairs will be in positions that are as far apart from one another as possible.
it is base on purely on the notion that electrostatic repulsions between entities consisting of two or more electrons dictate molecular geometries.
21
Q
What are the bond angles between groups of a linear arrangement
A
a linear arrangement has bond angles of 180 degrees between one another.
22
Q
When does a molecule have a trigonal planar arrangement?
A
A molecule has a trigonal planar arrangement when the central atom is attached to three groups, the bond angles are approximately 120 degrees between bonding groups.
23
Q
When does a molecule have a tetrahedral arrangement?
A
A molecule has a tetrahedral arrangement when the central atoms is attached to four groups, the bond angles between each group are between 109.5 degrees.
24
What is special about lone pairs in the VESPR theory?
Lone pairs are considered to be larger then electronic covalent bonds and therefore induce the bond angles to be smaller because larger groups are suspected to cause more repulsion between bonding groups
25
Where does Steric Repulsion arise from in Organic Chemistry?
Steric Repulsion arises from filled orbitals that cannot participate in bonding, the negative electrostatic field of the electrons in the orbitals is repulsive.
26
Describe the orientation of s and p orbitals
s orbitals are spherical and dont have any directionality
| p orbitals are lobes that are oriented at 90 degrees with respect to one another .
27
What is a qualitative description of Orbital overlap that results in Hybridization?
A qualitative description of molecular overlap is the degree at which orbitals occupy the same space. Regions of overlap have matched and mismatched phasing.
Opposite phasing cancels, matched phasing reinforces the overlap.
28
What is hybridization?
Hybridization is the method of adding and subtracting atomic orbitals on the same atom.
29
What does decreasing s character due to bond angles of hybridized orbitals?
Decreasing s character decreases bond angles.
30
The Formula used to find the fraction p character of hybridized orbitals is what?
1+icos(theta)=0
| theta is the observed angle, we use the observed angle to solve for i which is sp^i
31
Why is the magnitude of 12C-1HNMR coupling constants expected to be proportional to the amount of carbon s character in a bond?
The magnitude of 12C-1HNMR coupling constants is expected to be proportional to the amount of carbon s character in a bond because s orbitals have density at the carbon nucleus and can affect neighboring nuclear spin states,
32
where does the concept of binding energy primarily arise from?
Binding energy primarily arises from exchange (resonance) of electrons between the two atoms in a bond.
33
How do Sigma Bonds result?
Sigma bonds result from the overlap of one hybrid orbital with the hybrid orbital of another atom or the s orbital of a hydrogen atom.
34
How are pi bond created?
pi bonds are created by the overlap of two p orbitals of adjacent atoms.
35
describe the location of electron densities of sigma and pi bonds?
sigma bonds are noted to have their electron densities located along the nuclear/ bond axis while pi bonds are noted to have their electron densities located above and below the nuclear/ bond axis.
36
What is a bonding orbital vs an antibonding orbital?
A bonding orbital is the combination of two orbitals on adjacent atoms that results in in-phase interactions.
An antiboding orbital is the combination of two orbitals on adjacent atoms that result in out-of-phase interactions.
37
Which has more energy, the bonding or antibonding orbital?
The bonding orbital has less energy than the antibonding orbital.
38
What are non bonding orbitals?
non-bonding orbitals are those that are not bonding or antibonding, they are known to only contain lone pairs of electrons.
39
what is the bond order described as?
the bond order is described as the number of bonds between two atoms.
40
What is a polar covalent bond?
A polar covalent bond is a covalent bond tat has an unequal sharing of bonding pair electrons.
41
A polar bond is stronger or weaker then a less polar bond?
More polar bonds are stronger then less polar bonds.
42
What is electronegativity?
Electronegativity is the power of an atom in a molecule to attract electrons towards itself. The scale derived by pauling depends upon molecular properites and is not an intrinsic property of the atom(s).
43
What is ionization potential?
ionization potential is the energy required to remove an electron from an atom or molecule; ionization potential therefore reflects the affinity of the atom for the electrons it already has.
44
What is electron affinity?
Electron affinity is the amount of energy released or required to attach another electron to an atom or molecule.
45
What is the major factor influencing electronegativity and the associated trend?
The major factor influencing electronegativity is the energy of the orbitals that the atom in question uses to accept electrons
The valence orbitals become lower in energy as we move left to right across the periodic table and become higher in energy as we move down the periodic table.
46
What controls reactivity?
Reactivity of molecules is controlled by transition states.
47
What is an inductive effect?
Inductive effect is the potential to withdraw electrons through sigma bonds to a more electronegative atoms or group.
48
What is the field effect?
The field effect is the polarization in a molecule that results from charges that interact though space, rather than through sigma bonds, and can influence the structure and reactivity of other parts of the molecule.
49
Why are the bond angles of N-H n H-O-H reduced relative to methane.
Since lone pairs of these central atoms will not be shared with other atoms, lone pair electron orbital tend to have more s character (to hold it closer to the nucleus) giving the O-H bonds more p character reducing the bond angles.
50
Is it harder to withdraw electrons from p orbitals or s orbitals?
s orbitals are harder to withdraw electrons from because they reside closer to the nucleus
51
What is a bond dipole?
A bond dipole is a local moment that is associated with a polar covalent bond. it provides a means of comparing which bonds are polar and evaluating the relative force that a dipole exerts on neighboring charges or dipoles.
52
What is a moment?
A moment reflects the electrostatic force that would be exerted by a charge on a neighboring molecule.
53
What is a debye?
A debye is a unit used to reflect a dipole moment. It is expressed by charge times distance or electrostatic units.
54
What is a molecular dipole?
A molecular dipole is a well dfined intrinsic property of a molecule. it is a vector sum of all the individual dipoles within a molecule.
55
What is a quadrapole?
A quadrupole is simply two dipoles alighned in such a way that there is no net dipole, if their is a net dipole we have a dipole, not a quadrapole.
56
monopoles look like ___ orbitals
Quadrapoles look like ____ orbitals
Octupoles look like ___ orbitals
monopoles look like s orbitals
Quadrapoles look like d orbitals
Octupoles look like f orbitals
it is important to note that orbitals dont have polar character, the analogy (comparison) is used to illustrate phasing properties
57
What is a resonance structure?
A resonance structure is one lewis illustration that participates in the hybrid that makes up the actual molecule.
58
What is resonance?
The practice of superposition resonance structures to describe the bonding properties of a molecule.
59
What is delocalization?
Delocalization is implying that electrons are covering a larger number of atoms than given by any one resonance structure.
60
What is resonance or delocalization energy?
Resonance or delocalization energy is the energy of stabilization imparted by resonance. the reason they are more stable is because the more spread out the orbital is that electrons occupy, the lower the energy of these electrons.
61
is the nitrogen in pyrole sp2 or sp3 hybridized?
the nitrogen in pyrole is sp2 hybridized because it wants to maximize the number of resonance structures it has to promote stability and it does this by placing its lone pairs in a p orbital to participated in a conjugated pi bond system with multiple resonance structures.
62
bonding with atoms with larger atomic radii results in shorter or longer bond lengths.
The larger the atomic radii, the longer the bond lengths typically are.
63
How does hybridization effect bond length.
The more s character a atom has for its hybridization, the shorter the bond length since electrons are held closer to the nucleus, the more p character an atom has for its hybridization, the longer the bond length since electrons are held farther away on average from the nucleus.
64
What are the three different kinds of radii used to understand molecular dimensions
The three kinds of radii uses to understand molecular dimensions are: covalent, ionic, and van dear walls radii
65
As positive charge increase, radii ________ for an ion
| As negative charge increases, radii ________ for an ion
As positive charge increases radii decreases For that of an ion
As negative charge increases, radii increases for that of an ion
66
What is the van dee walls radii
Van der walls radii of an atom is the effective size of the electron cloud around an atom when in a covalent bond, as perceived by an atom to which it is not attached.
67
What is polarizability.
Polarizability is the ability of an electron cloud to distort in response to an electric field
68
Polarizability trends on a periodic table
As you go from left to right across a periodic table, atoms become less polarizable.
As you go from top to bottom in a column on a periodic table atoms become more polarizable
69
What are group orbitals?
Group orbitals are orbitals that are delocalized over a defined group of atoms
70
What is angle strain?
Angle strain is any strain that is derived from non standard bond angles
71
What is a reaction coordinate?
A reaction coordinate is the weighted average of all the available pathways for a chemical reaction
72
What is the reaction coordinate diagram?
A reaction coordinate diagram is a two dimensional plot of the reaction coordinate with geometrical coordinate as the x axis and the energy as the y axis
73
What is the transition state on a reaction coordinate diagram
The transition state on a reaction coordinate diagram is the highest point on the lowest energy pathway inter converting the reactant and the product
74
What is a relatively stable structure depicted as in a reaction coordinate diagram.
A relatively stable structure in a reaction coordinate diagram is depicted as a low energy depression in the curve .
75
How are reactive intermediates depicted in a reaction coordinate diagram?
Reaction intermediates in a reaction coordinate diagram are depicted as high energy depression or high energy shallow wells between transition state peaks
76
When is a structure considered to be a transition intermediate rather than a transition state?
A structure true is considered to be a transition intermediate rather then a transition state when the structure in question exist for longer then that of a typical bond vibration 10^-13 - 10^-14 seconds
77
The longer the barriers leading to and from each well...
The longer the lifetime of the structure represented by the depression in the curve.
78
What is the rate determining step in a reaction coordinate diagram?
What does the rate determining step represent?
The rate determining step in a reaction coordinate diagram is related to the overall barrier height between the reactant and the hieghest energy transition state.
The rate determining step determines the overall rate of product formation.
79
What is the principle of least motion?
The principle of least motion is used for drawing reaction coordinate diagrams for complex reactions. It favors reactions that involve the least amount of change of nuclear position or electronic configuration. Even though the overall process involves a dramatic change in nuclei positioning or electronic configuration, this is normally done is a series of steps
80
For reaction coordinate diagrams the kinetic product is the one where....
The thermodynamic product is.....
The kinetic product is the one where the intermediate structure has to overcome the smallest energy barrier while the thermodynamic product is the one where the overall product had the lowest energy state (configuration)
81
When drawing double bonds, what do we need to make sure we do?
Make sure to draw all the atoms attached to the sp2 hybridized atoms in the same plane and draw either the side view or the top view, not a combination of the two.
82
Are Alkenes with electron donating groups at the alpha position to the double bond electron rich or electron deficient, explain.
Alkenes with electron donating groups at the alpha position to the double bond are electron rich due to donation of electron density by resonance with lone pairs and the pi bond.
83
Make sure to use the correct arrows when describing resonance and equilbrium
is resonance is equilibrium
84
what are the names of the carbonyl, alcohol, and carbonate forms of the tautomerization for ketone.
Keto, Enol, and Enolate group
85
Are charged nucleophilies more reactive than those that are neutral?
charged nucleophiles are more reactive than those that are neutral with respect to kinetics.
86
what metal ions are known to stabilize enolate compounds?
Enolate compounds are typically stabilized by dissociated salt components such as Li, Na, and K
87
When will a chemical shift go upfield for a carbon or hydrogen?
A chemical shift will go upfield when there is more electron density concentrated at that carbons particular nucleus because increased electron density increases shielding effects.
88
is pulling out an electron an oxidation or a reduction?
pulling out an electron is an oxidation, not a reduction. To be reduced means to receive electrons, to be oxidized means to give electrons.
89
which is higher in energy? the LUMO or the HOMO
The LUMO is higher in the orbital energy diagram than the HOMO.
90
Where do electrons get added during reduction and get removed during oxidation reactions?
Electrons get added to the LUMO during reduction reactions and removed from the HOMO during oxidation reactions.
91
What is an Umpolung reaction?
An Umpolung reaction is one where the chemistry for a molecule inverts due to some alteration of the electron structure
92
What is an example used in lecture of an umpolung product?
Pulling out an electron from an alkene with an electron donating group on an attached sp2 carbon causes the originally nucleophilic alkene to become electrophilic.
93
Molecules that undergo umpolung conversion by removal of an electron can undergo what kind of reaction?
molecules that undergo umpolung conversion from an nucleophile to an electrophile, like an alkene with an electron donating group, can dimerize
94
What is the symbolism for an electron donating group? What is the symbolism for an electron withdrawing group?
An electron donating group is X while an electron withdrawing group is Z
95
Adding an electron (reduction) to an alpha, beta, unsaturated carbonyl compound causes what kind of conversion to occur?
adding an electron to an alpha, beta, unsaturated carbonyl compound causes an umpolung conversion to occur from an electrophile the beta position, to a nucleophile at the beta position
96
what are the possible electron donating groups for a ring, and where does it cause electrophilic constituents to add?
Electron donating groups are -NR2, -OR, methyl, -SR, PR2, and halogen groups. They donate with there lone pair electrons
97
What does a homolytic bond cleavage produce?
A homolytic bond cleavage produces two radicals R-R --> R* + R*
98
What information does the bond dissociation energy provide?
The bond dissociation energy provides information about the bond strength and the enthalpy for a reaction.
99
why is forming cyclic structures energetically (entropitically) unfavorable?
Forming cyclic structures is unfavorable because sigma bonds are frozen, they are not free to rotate, eliminating many degrees of freedom for the bond.
100
Shorter bonds are stronger bonds, what does this mean in regards to its bond dissociation energy?
Shorter bonds are stronger bonds, more electronegative atoms produce short bonds. This means there is more energy stored within the bonds. The bond dissociation energy will be larger.
101
Do bonds become weaker or stronger as the constituent attached to the carbon moves down he periodic table?
Bonds become weaker as the constituent attached to carbon moves down the periodic table because the larger orbital leads to a size mismatch, leading to less overlap, which means less orbital mixing, which means a weaker bond.
102
What are the units of enthalpy?
units of enthalpy are kcals/mol
103
it is an endothermic reaction when.
It is an endothermic reaction when, the products have less energy stored within their bonds then the reactants.
104
When do strain energies seen between rings see a drastic decrease in strain energy?
when the number of constituent atoms in the ring is 6 or greater we see a large decrease in strain energy.
105
When do rings start become indistinguishable from linear chain structures, not having much strain energy?
When n >= 17 rings become so large that they are barely distinguishable from linear chains.
106
What is transangular strain, and when does it typically occur?
Transangular strain occurs for medium size ring compounds 8-10 = n
rings that lie across the ring from one another tend to orient themselves vary close to one another in space, this leads to substaintal torsion and bond distortion.
107
What is baeyer (angle) strain?
Baeyer or Angle strain, is an strain that arise primarily from non-standard bond angles.
108
What is pitzer strain?
Pitzer strain is strain in cyclic systems that arises do to torsional strain, strain that results from carbons on opposite faces of the ring being in close proximity to one another.
109
Why arent the bond angles in cyclobutane 90 degrees, why is eclipsing C-H bonds along the C-C an unfavorable situation? Why isnt the compound planar?
Cyclobutuane isnt planar because puckering promotesC-H bonds from eclipsing with one another, this cause bond angles between carbons to deviate by two degrees.
110
What is butterfly motion?
Butterfly motion is the inversion of a ring to interconvert the two puckered forms of a cyclic compound. The cyclic compound is puckered to avoid steric interactions between flagpole hydrogens.
111
what is the heisenburg uncertainity principle?
In quantum mechanics, the uncertainty principle is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle known as complementary variables, such as position x and momentum p, can be known simultaneously. For instance, in 1927, Werner Heisenberg stated that the more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa.[1] The formal inequality relating the standard deviation of position σx and the standard deviation of momentum σp was derived by Earle Hesse Kennard[2] later that year and by Hermann Weyl[3] in 1928
112
What is a stereoelectronic effect?
A stereo electronic effect is about the relative orientation (or stereochemistry) of electronic orbitals
113
What is the anomeric effect?
The anomeric effect is a stereoelectronic effect that stats that the placement of lone pairs antiperiplanar to polarized bonds, or trans, is found to be stabilizing. lone pairs can also enhance the departure of a leaving group is they are arranged antiperiplanar to it. co planar, often at 180 degrees.
114
In elimination reactions, what is the most acidic hydrogen?
The most acidic hydrogen in an E1 reaction is the one that is lined up with the empty p orbital, the one that is aligned in hyperconjugation.
115
For E2 reactions, there is a strong influence from stereo electronic factors. E2 reaction as a double bond character in the transition state. The p orbitals in the double bond must be conplanar in the product, which orientation is best. antiperplana or synperiplanar for E2 reactions.
Syn periplanar require a transition step because the orbitals are filled sigma bonding orbitals are not oriented with respect to one anotther, staggered in line to eachother and must adjust their stereoarrangement to form the pi bond. there is better anti bonding orbital overlap between the C-H bond that is being deprotonated and the C-X bond that is breaking.
116
When does syn occur before anti elimination?
Syn elimination will occur over anti elimation when a synperiplanar arrangement can be obtained while an antiperiplanar arrangement cannot be obtained. The counter ion of the base deprotonating the alkane is aiding the leaving group. Strong steric factors favor the syn pathway.
117
What do you consider when trying to deduce changes in entropy for organic reactions?
Entropy decreases when the products being formed are less then the reactants
Entropy decreases when an atom that is attached via a sigma bond, its attached to an atom that is sp2 hybridized because is has to exist within the plane of the sp2 hybridized atom it is then bound to.
118
For CH2 the triplit state is preferred over the singlet state, true or false?
The triplit state is preferred over the singlet state until the distortion of the angles between two hydrogens causes them to come close enought to one another in proximity that it is energetically favorable for both electrons to occupy the same molecular orbital with opposite spins.
119
Where do harder nucleophiles attack alpha beta unsaturated carbonyl compounds? where do softer nucleophiles attack?
Harder nucleophiles attack the carbonyl position because harder nucleophiles tend to bear counter ions that stabilize the transtion state/ structure and lead them to the electrophilic center
Softer nucleophiles attack the beta position because the largest orbital character in the LUMO exists in the Beta carbon
120
What are baldwins rules? or the three rules that allow chemists to predict the ease of ring closure reactions?
The three rules to consider are
1. ring size
2. hybridization of the carbon undergoing attack
3. whether the bond will be endo or exo cyclic to for the ring in the product
endo if the cation, radical, or anion exist within the ring after intramolecular addition
exo if the cation, radical, or anion exist outside of the ring after intramolecular addition.
121
What is the terminology for cylic addition
```
dig = sp carbon undergoing attack
trig = sp2 carbon undergoing attack
tet = sp3 carbon undergoing attack
```
5-exo-dig cyclization
122
What is a radical clock?
A radical clock is the time it takes for an intramolecular free radical arrangement to occur. it is a experimentally determined measurement that is dependent on environmental conditions such as temperature
123
What is the point of incorporating radical clocks into molecules?
The point of incorporating radical clocks into molecules is to show whether or not radical intermediates do or do not exist, and if they do determine the life time of the intermediate relative to the clock.
