Week 1 Flashcards
Molecules have a shape what type of shapes ?
Some simple molecules maybe linear (one-dimensional) or planar (two-dimensional). or three dimensional. most are three dimensional
what the ways to predict a shape?
Yes. For covalent compounds of the s-andp-blocks (including organic chemistry),we can use VSEPR.
for transition metals we can use d and f blocks
VSEPR
VSEPR stands for Valence Shell Electron Pair Repulsion. Sometimes referred to as VSEPR Theory.It is based on the assumption that electr on pairs repel each other.Only appropriate for s-and p-block compounds.
Note
Note that VSEPR is a simple model for predicting structures. It is not a good model for understanding electronic structure.
4 valence electrons
tetrahedral
109.5
3 valence electrons
trigonal planar
120
2 valence electrons
linear
180
tetrahedral chiral
when all four atoms around the carbon are different,VSEPR still predicts a tetrahedral structure but the molecule is now chiral.A chiral molecule comprises a pair of non-superimposable mirror images.MoreonthisfromJonathanClaydenlater.
tetrahedral chiral
when all four atoms around the carbon are different,VSEPR still predicts a tetrahedral structure but the molecule is now chiral.A chiral molecule comprises a pair of non-superimposable mirror images.
5 valence electron
1 lone pair of electrons
trigonal pyramidal
107
lone pair of electrons
lone pairs repel more than bond pairs because they are only associated with the central atom. The H–N–H angles are therefore less than 109.5° and are about 107°.
6 valence electrons
2 lone pairs
bent
104.5
6 valence electrons
octahedral
7 valence electron
one lone pair
square-based pyramid
8 valence electrons
two lone pairs
square planar
cis and trans
octahedral
square-based pyramid
square planar
All vertices in an octahedron are equivalent by symmetry.In BrF5 ,there is no choice as to where the lone pair goes.In XeF4 ,the two lone pairs could be cis or trans; they go trans as this means they are further apart
video
cis and trans
fac and mer
double bonds
4 valence electrons
linear
180
6 valence electrons
bent
104.5
one double bond
3 single bonds
one lone pair
trigonal bipyramidal.
hybridisation
bonds between s shell and one or more p valence electron
octet rule
how two valence electrons in S and 6 valence electrons in p (1 orbital 3 orbital) are involved in bonding in covelent reactions.
covalent bonds with fewer electrons in valence orbitals are called
electron deficient
8 electrons will
fill bonding and non-bonding orbitals
v shaped
one electron alone
Optically active molecules which rotate plane-polarized light in a counterclockwise direction are said to be
levorotary
Optically active molecules which rotate plane-polarized light in a clockwise direction are said to be
dextrorotary
Optically active molecules which rotate plane-polarized light in a clockwise direction are said to be
dextrorotary
The specific rotation of a compound is denoted by the symbol:
[alpha ]d
diastereomers
diastereomers are not mirror images of each other and non-superimposable.
how to calculate stereoisomers
2 ^n n is the number of stereogeneric carbons
stereogeneric
that is, having at least two different groups bound, interchanging any two different groups would create a stereoisomer
meso
Meso implies that there is one or more stereogenic centers on a molecule
meso
not active
mirror image
plane of symetry
two or more chiral centre
