chemistry general revision (pt2) Flashcards
what are the steps of free readical reactions and what hapens in each step ?
-
Initiation
- homolitic fragmenetation of a weak bond in order to form 2 new free radicals -
Propagation
- more free radicals are produced
- redicals collide with alkane and removes H
- chain reaction continues endlessley in a cycle -
Termination
- free radicals are disrupted when there is a significant radical-radical combination reactions
what type of reaction is a free readical recation ?
a chain reaction
what is a condensation rection ?
a reaction in which 2 or more molecules combine into 1 molecule whilst also loosing a small molecule (e.g. water)
what is a hydrolysis reaction ?
a reaction wehre a molecule breaks down is smaller molecules with the help of another molecule (such as water).
nature of free radicals
5
- they are unstable
- short lived
- react very quickly
- exposed to intense ultra-violet radiation from the sun
- form and destroy the ozone layer
nature of a nucleophile
- Can donate electrom pairs
- Either negatively charge or neutrally charged
- undergo necleophillic addition and subtraction
- Also called Lewis bases
nature of eletrophiles
- can accept an electron pair
- either positively charged or neutrally charged
- either electrophillic addition or substitution reaction
- also called Lewis Bases
name structural isomers
they are 3
- chain isomers
- functional group isomers
- positional isomers
what is a chain isomer ?
A different arrangement of a molecule’s carbon skeleton
- rearranging the carbons can give branched carbon chains coming off the main chain, the name of the moclecule rflects this but fomula remains the same
- similar chemical properties and slightly different physical properties
what is a positional isomer ?
Different position of the same functional group in the molecule
* molecular formular remians the same, functional group also remians the same
* the name of the molecule chnages to refekct the posotion of the fucntional group
* similar chemical properties and slightly different physical properties
what is a functional group isomer ?
Differing postion of atoms give different functinal groups
* same molecuar formula but atoms re rearranged to give a different functional group
* name of the molecule chnages to reflect the new functional group
what are the 2 STEREOISOMERISMs ?
- optical isomers
- geometrical isomers
What are Geometrical Iosmers ?
- Different substituents around a bond with restricted rotation
-
Molecules with the same molecular formula and structural formula, but different shapes
* most common geometrical isomers are alkenes and cyclic compunds
* sometimes refered to as cis-trans isomers
* atoms in single covalent bonds in open chain compounds are able to undergo free rotation with respect to other
* distinct compounds with different physical properties melting points, boiling point and spectroscopic properties
what is E configuration in gemotrical isomers ?
E configuration – the highest priority groups are on the opposite side of the double bond
highest priority = highest atomic number
what is Z configuration in geometrical isomers ?
Z configuration = The highest priority groups are on the same side of the double bond
what are optical Isomers ?
Non superimposable mirror images of the same molecule
What is a CIS-ISOMER ?
Similar functional groups on the same side
what is a TRANS-ISOMER
Similar functional groups on oppossite side
Meaning of Achiral
object that can be superimposed on its mirror image
Meaning of Chiral
Object is one that cannot be supermiposed on its mirror image
meaning of configuration R
clockwise
meaning of configuration R
clockwise
meaning of configuration S
anticlockwise
