Exam 3 Flashcards
two factors that tell us of a reaction is favorable
thermodynamics: is there enough energy?
kinetics: how fast?
enthalpy
- ΔH or q
- heat energy exchange between a reaction and it surroundings at a constant pressure
- also the amount of energy required to form or break bonds
endothermic
- ΔH>0
- energy is required from surroundings
- temperature decreases during reaction
exothermic
- ΔH<0
- reaction gave up energy the the surroundings
- temperature increases during reaction
entropy
- ΔS
- amount of disorder or randomness
ΔS<0
multiple molecules come together to form a smaller number of molecules
ΔS>0
smaller number of molecules break apart to form a larger number of molecules
gibbs free energy
- 🔼G
- measures spotaneity of a reaction by taking entropy and enthalpy into account
what does a negative 🔼G say about the reactants and products?
the reaction favors the products
factor affect reaction rate
- concentration of reactants
- Activation energy
- temperature
- geometry and sterics
- presence of a catalyst
What levels of activation energy are favorable?
small AE
what does A stand for in k=Ae^(-Ea/RT)
a factor taking geometry into consideration
what allows temperature to influence the rate of the reaction?
temperature affects the rate constant
transition state
- an energy maxima on a reaction pathway
- barely exist for a moment, cant be observed
- bonds are in the process of being broken and formed
- unstable af
exergonic reaction
- products are favored at equilibrium
- spontaneous
- products have lower amount of free energy than reactants
- 🔼G
- Keq>1
endergonic reaction
-reactants favored at equilibrium
-nonspontaneous
-products have more free
energy than reactants
-+🔼G
-Keq<1
intermediate
- state occurring at an energy minimum
- usually exist long enough to be observed
- bonds are not in the process of forming and breaking
- species are fully formed and can be isolated
which points on energy diagrams are structurally similar?
points that are close to each other
Hammond postulate
- In an exergonic process, the transition state is closer in energy to the reactants and therefore is more structurally similar to the reactants
- in an endergonic process, the transition state is closer in energy to the products and therefore more structurally similar to the products
nucleophile
- loves attacking nuclei
- atoms that carry partial negative charges, an available pair of electrons or a pi bond
- large atoms
- ARE electron dense
electrophile
- electron loving
- electron deficient
- can accept a pair of electrons, or has a + partial charge
- carbocations
what makes nucleophiles have have nucleophilic characteristics?
polarizability: ability of an atom to distribute its electron density unevenly in response to external influences
Which atoms can have a + charge and not be electrophiles?
O+ or other atoms with 4 bonds that would exceed the octet rule if the
nucleophilic attack
- has forms with 1 and 2 arrows
- nucleophile attacks an electrophile
- tails of arrows start on electron(- charge)
- head of the arrow ends on a nucleus(+ charge)
- electrons are shared, not transferred