Lecture 4 Flashcards
bond angles vary with?
size of substituent
what does a higher electronegativity on the oxygen atom mean?
the lone pair of electrons on the oxygen atom is less likely to be protonated than those on the nitrogen atom.
bonding molecular orbitals and antibonding molecular orbitals.
- bonding molecular orbitals = less energy than parent molecular orbitals
- antibonding molecular orbitals = more energy than parent molecular orbitals.
atomic orbitals combine most effectively to molecular orbitals if…
they have similar shape and energy
bond order equation
bond order = (electrons in bonding MO - electrons in antibonding MO)/2
molecular oxygen in increasing energy
ground state triplet, ground state singlet, excited state singlet
multiplicity of energy levels equation
M = 2S + 1
S = sum of spin values in highest occupied molecular orbital (HOMO)
what does the molecular orbital theory predict about oxygen?
molecular oxygen is a diradical
- a molecular species with 2 electrons occupying 2 degenerate molecular orbitals.
what does the loss of an alcohol function mean?
it does not negate biological activity
what does the loss of an amino group mean?
results in loss of biological activity
what are alcohols with 2 or 3 hydroxyl groups known as ?
diols (glycols) or triols
what are hydrocarbons with more than 3 hydroxyl groups knows as?
polyols (e.g carbohydrates)
why are phenols much stronger acids than alcohols?
due to delocalisation of the negative charge on the conjugate base (phenoxide ion)
what properties does a more acidic phenol have?
good antibacterial properties
(e.g. triclosan, which is added to toothpaste and household detergents due to its antibacterial action.)
phenols are…
special alcohols and antioxidants
homolytic and heterolytic
- homolytic = oxidation
- heterolytic = ionisation
what happens when the phenoxy radical preferentially tends to dimerse?
it terminates the radical chain reaction
ethers properties
- much less polar than parent alcohols
- formerly used in anaesthesia (diethyl ether) before non-flammable homologues were discovered to have similar biological activity (haloethane) by reacting with nerve cell membranes.
- ethers are liable to have potentially explosive epoxides in presence of molecular oxygen and UV light.
cyclic ethers are known as…
epoxides
why are 3 membered ring epoxides highly reactive?
because of torsional strain.
what are commonly found in the structure of drug molecules?
ketones
why are aldehydes less commonly found in the structure of drug molecules?
because of their higher reactivity towards nucleophiles
how are aldehydes found?
in the open chain form of reducing sugars
what does the high reactivity of aldehydes result in?
general cytotoxicity
