Test 2 Flashcards
What is an atom?
the smallest particle of an element.
How are the atomic numbers structured?
How to calculate with atomic amu? example 6 protons and 6 neutrons.
The principal quantum number (n)
Azimuthal quantum number (l)
value of l: 0 1 2 3 4 …..
letter designation: s p d f g …..
n=1 → 1s
n=2 → 2s 2p
n=3 → 3s 3p 3d
n=4 → 4s 4p 4d 4f
Magnetic quantum number (m)
Values from 1- to +1
S orbital m = 0 => 1 orientation
P orbital m = -1, 0, +1 => 3 orientations
D orbital m = -2, -1, 0, +1, +2 => 5 orientations
Noble gases
None of them react, noble gas is stable
All have filled valence energy (8 valence electrons) except He that has only 2
Chemical bonds
Atoms ionize and transfer electrons (ionic bonds) or share electrons (covalent bonds) in order to reach Noble Gas electron configuration. (octet rule)
When do covalent bonds form?
when two atoms share valence electrons.
When do polar covalent bonds form?
when two atoms share valence electrons
unequally.
One end of the bond has a fractional negative charge and the other a positive charge
When do ionic bonds form?
when one atom donates or transfers valence electrons to
another atom.
What is electronegativity?
the tendency of an atom to attract electrons towards itself.
Molecular orbitals(MO)
mathematical function describing the wave-like behavior of an electron in a molecule.
σ MO and σ* MO
Sigma bond, strongest type of covalent bond
electrons spend most of
their time in the region directly between the two nuclei.
and
electrons spend
most of their time away from the region between the two
nuclei.
π MO
Pi bonds
are formed by side-ways (lateral) overlapping
between p atomic orbitals
Structure of methane
CH4, sp3, σ bonds
Structure of ethane
C2H6, two overlapping sp3, σ bonds
Structure of ethene
C2H4, three sp2, σ bonds
Structure of ethyne
C2H2, two sp, σ bonds
Cis and trans isomers
Hydrocarbon classifications
Alkanes -> single bond -> -ane
Alkenes -> double bond -> -ene
Alkynes -> triple bond -> -yne
Aromatics -> rings
Classification of carbon atoms in alkanes
Primary carbon - one carbon neighbor
Secondary carbon - two carbon neighbors
tertiary carbon - three carbon neighbors
quaternary carbon - four carbon neighbors
What are Van der Waals forces?
intermolecular forces, such as the covalent bonds that hold atoms
together in molecules
hold molecules together in a liquid or solid
weaker than covalent bonds
(Van der Waals) Dipole - dipole interaction
Molecules arrange themselves with positive and negative ends towards each other. (attraction) because they move freely in a liquid they experience both attraction and repulsion interactions simultaneously.
(Van der Waals) London dispersion forces
Temporary fluctuations in the
electron distributions within
atoms and nonpolar molecules
could result in the formation of
short-lived instantaneous dipole
moments, which produce
attractive forces between otherwise nonpolar substances.
(Van der Waals) Hydrogen bond
A hydrogen bond is an attraction between two atoms that already participate in other chemical bonds. One of the atoms is hydrogen, while the other may be any electronegative atom, such as oxygen, chlorine, or fluorine.
Halogenation of alkanes
Ex.
CH3CH2Cl - chloroethane (ethyl chloride)
Stability of the free radicals (alkanes) and same case for carbocations (just add positive charge to carbon)
3* > 2* > 1* > methyl
alkane halogenation - radical chain reaction
Cycloalkanes general formula
Get the prefix cyclo- before the names
CnH2(n+1-g)
n = number of C atoms
g = number of rings in the molecule
Cyclohexane non-planar conformations
chair (most stable)
boat
twist boat
half chair
What is benzene?
Benzene is an organic chemical compound with the molecular
formula C6H6 (think of satan)
Flat ring of sp2
It has six π electrons
Benzene - electrophilic aromatic substitution
Benzene derivatives
1,2-dichlorobenzene
1,3-dichlorobenzene
1,4-dichlorobenzene
what are Stereoisomers?
have their atoms connected in the same sequence, but they differ in the arrangement of their atoms in
the space.
When is an object chiral?
an object is chiral when its mirror image is different from the original
object. (left and right hand)
What are enantiomers?
Molecules with the same mirror image
What are diastereomers?
Molecules that are not mirror images of each other. (cis-trans, conformers)
chirality center
Guarantees the molecule is chiral
- has four different groups attached
R or S enantiomer?
Lewis acid
accepts an electron pair (an electrophile)
and has vacant orbitals.
Lewis base
donates an electron pair (a nucleophile)
and has lone-pair electrons.
nucleophile
a species with an unshared electron pair, reacts with an alkyl halide by replacing the halogen substituent.
Nucleophilic substitution reaction
SN2 reaction
SN1 reaction
