TEST BANK For Organic Chemistry Mechanistic Patterns, 2nd
Edition by Ogilvie, Ackroyd, Verified Chapters 1 - 20, Complete
Newest Version
What is hybridization? - ANSWER: The mixing of atomic orbitals to give new
hybridiised orbitals
how are sp orbitals formed? - ANSWER: mixing 2S and 2P , gives two SP hybrid
orbitals arranged along the x axis.
These are 50% S charcater and 50% P character.
How are sp2 hybrid orbitals formed? - ANSWER: mixing 2s and two 2P orbitals gives
3 SP2 orbital arrannged in a plane at 120 degrees to each other. They have 33% S
character and 66% P character
How are SP3 orbitals formed? - ANSWER: mixing 2s, 2px,2py and 2pz orbitsl together
forms 4 SP3 orbitals arranged in tetrahedral shape 109 degrees to each other. They
have 25% S charcater and 75% P character.
Why are bonding orbitals lower in energy than atomic orbitals ? - ANSWER: Bonding
molecular orbitals are lower in energy than atomic orbitals because they have
increased stability assosiated itg the formation of the bond. Bonding orbitals are
formed via constructive interference which is the overlap of 2 peaks which stablaises
and lowers in energy
electron density between the orbitals ( think of photo)
Why are anti bonding orbitals higher in energy? - ANSWER: Anti bonding orbitals are
higher in energy than atomic orbitals because they are formed via destructive
interference( caused by a peak and a dip overlapping and cancelling out)This
destablaises and increases them in energy
no electron density between orbitals (think of photo)
------ orbital ---- electon interactions are stablaising -filll in the gaps - ANSWER: Two
orbital two electeron interactions are stabalising
what does stabalising mean ? - ANSWER: Stabalising means lowering in energy
What distance apart should an empty atomic orbital and filled atomic orbital be to
have the greatset stabalisation of the molecular orbital?(when two atomic join to
form molecular orbitals) - ANSWER: The stabalisation is greatsest if a filled orbital
and an empty obrital are closer in energy.
Closer in energy = greatsest stabalisation = molecular bonding orbtial will be lowered
further in energy
,What must interacting orbitals have in order to interact well? - ANSWER: Interacting
rbitals must have good alignment and be able to overlap effiencelty. This means they
must be able to approach each other and be of comparable size. They must also
have matched symmetry
Give a example of when orbitals are not able to interact effciently - ANSWER: At the
bridgehead of two small rings a double bond caanot be formed - known as Bredt's
rule. This occurs as the orbitals at the bridgehead are perpindicular to each other
and cannot overlap
What does the activation energy tell us ? - ANSWER: gives us the rate of reaction at a
given concentration
What is the symbol for activation energy ? - ANSWER: ΔG‡
What does free energy change give us ? - ANSWER: determines the position of
equilibirum
What is the symbol for free energy change - ANSWER: ΔG°
What is the rate determining step? - ANSWER: the rate determining step is the step
with the highest energy barrier
Compare transition states and intermediates - ANSWER: Transition states have
patially formed bonds, intermediates have fully formed bonds
Transition states do not exist for a finite time and cannot be isolated or observed,
intermediates exists between energy barriers and can be observed and isolated.
What are transition states - ANSWER: They have partially formed bonds and appear
as a maxima on a free energy diagram
Why are transition states high in energy ? - ANSWER: They are high in energy
because they are unstable, reactants dont stay there for long but move quickly to
the next step of the chemical reaction.
What are intermediates ? - ANSWER: Intermediates are the product of one reaction
and the reactant of another , they have fully formed bonds.
Equation for change in gibbs free energy (using enthaly and entropy) - ANSWER: ΔG°
= ΔH° - TΔS°
where ΔG° - change in gibbs free energy
ΔH°- change in enthalpy
T - temperature in Kelvin
ΔS°- change in entropy
, What must ΔG° be for products to be favoured? - ANSWER: For products to be
favoured over reactants at equilibirum , ΔG° must be negative
Equation for ΔG° using equilibirum constant - ANSWER: ΔG° = -RTlogeK
When does ΔG° determine the ratio reactantat products ? - ANSWER: when the
rreaction is under therodynamic control.
What is equilibrium ? - ANSWER: a state in which opposing forces or actions are
balanced so that one is not stronger or greater than the other. ( when the reactants
and products are at a constant - not nesecarily of equal concentraion)
In relation to K (equilibrium constant) will products or reactants be favoured in the
following examples
-when there a higher concentration of products than reactants at equilibrium
- when there is a higher concentraion of reacttants than products at equilibirum
- when there is eqaul concentration of products and reactants at equilibirum -
ANSWER: -when there a higher concentration of products than reactants at
equilibrium - K is more than 1 so logK is postivie meaning ΔG° is negative and
products are favoured
- when there is a higher concentraion of reacttants than products at equilibirum - K is
less than 1 so logK is less than 0 this means ΔG° is positive and so reactants are
favoured
- when there is eqaul concentration of products and reactants at equilibirum - no
change in gibbs free energy so niether products or reactants are favoured
Equation to calculate equilibirum constant - ANSWER: K=[products]/[reactants]
(concentrations)
In order for ΔG° to be negative what must be true ? - ANSWER: One of or both :
ΔH is negative
ΔS is positive
When would ΔH be negative ? - ANSWER: ΔH would be negative whenthe bonds in
products are stronger than the bonds in reactants or there is less strain in products
than reactants
When would ΔS be positive ? - ANSWER: ΔS would be positive when there is greater
freedom of motion (less order) in the products than in the reactants. - when entropy
is increased from reactants to products = more moelcules
How is charge delocalised by solvents? - ANSWER: A polar solvent will cluster around
charged in reactants and products (solvation) so that the charge is delocalised
How can solvents effect the equilibirum of a system ? - ANSWER: A polar olvents can
effect the energy of a system as it can stabalise charges through charge-dipole
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