Lecture 7 Flashcards
In the free radical mechanism how are bonds broken?
By Homoylsis.
What is homolysis?
Breaking of bonds into 2 equal parts.
Homoylsis is common in what type of bonds?
Non polar bonds.
No charge on atoms.
What is needed for a free radical mechanism?
U/V light- ENERGY
What happens in the initiation step in a free radical mechanism?
Radicals are produced.
What happens in the propagation step in a free radical mechanism?
Radials react with substrate- New radicals are produced so the reactions continues.
What happens in the termination step in a free radical mechanism?
Two radicals combine.
What happens in bond formation between radicals?
Each atom DONATES one electron to form a two- electron bond.
In fatty acid and prostaglandin biosynthesis what is needed to start the reaction?
What is produced? How?
Enzyme.
Radical is produced as hydrogen is removed.
Damage to DNA can cause CANCER. Small amounts of H2O2 in metabolism produce what radicals? Why?
OH radicals because of the weak O2 bond.
What substance prevent radicals from completing a harmful reaction? How?
Antioxidants.
Radical reacts with the antioxidant to form a stable radical so they don’t react with a biological molecule.
What enzyme has been developed to make use of reactivity of radicals?
CP450
In polar/ ionic mechanisms how are bonds broken?
Heteroylsis
In polar/ ionic mechanisms which atom to the electrons move to?
The most electronegative atom.
What is heterolysis?
One species takes both electrons.
What is an electrophile?
Electron lover/ Vacant Orbitals
Fully positive/ slightly positive.
What is a nucleophile?
Nucleus lover (Positive) Lewis bases or lone pair of electrons.
Are carbocations electrophiles/ nucleophiles? Why?
Electrophiles
Carbon centre is electron deficient.
Are carbanions electrophiles/ nucleophiles? Why?
Nucleophiles
Contain an electron- rich carbon centre.
How is the movement of electrons show?
Where does it start from?
Curly arrow
Starts with electrons to wherever they are going.
What is an addition reaction?
What happens to pie bond in these reactions?
Reaction where a SMALL molecule is ADDED to the starting material.
Broken.
What is an elimination reaction?
What happens to pie bond in these reactions?
Involves REMOVAL of atoms/ groups from 2 ADJACENT atoms in the substrate molecule.
Formed.
What is an oxidation reaction?
REMOVAL of H2 or INTRODUCTION of OXYGEN
What is an reduction reaction?
ADDITION of H2.
