Chem unit 2 Flashcards
Compounds with carbon and hydrogen atoms are called
hydrocarbons
Most important sources of hydrocarbons are
petroleum and natural gas
Long molecular hydrocarbons are
solids, small ones are the liquids and the shortest are gases.
ALIPHATIC: hydrocarbons
or open chain hydrocarbons. They are either straight chained or branched. They can be saturated (single bond) or unsaturated. (multiple bond)
AROMATIC: hydrocarbons
or closed chain (cyclic) compounds
The covalent bond between carbon atoms is (weak or strong)
very strong which is the reason behind long and stable chains in organic compounds. Carbon atom has 4 electrons in the valence shell which makes it neither a cation nor an anion. It shares electrons with other bonding atoms.
carbon cattion or anion?
niether
ALKANES: General formula is
CnH2n+2
ALKENES: General formula
CnH2n
ALKYNES: General formula is
CnH2n-2
AROMATIC COMPOUNDS: General formula is
CnH2n-6
benzene ring
C6H6
ALKYL HALIDES
are compounds where halogens replace the hydrogen atoms in alkanes. If H atom of methane (CH4) is replaced by a Cl atom, methyl chloride is formed. (CH3Cl)
alkanes undergoing combustion
to yield carbon dioxide, water and energy.
C3H8 + 5O2 –> 3CO2 + 4H2O
Alkanes undergoing halogenation
is a substitution reaction when exposed to very high temperature.CH4 + Cl2 –> CH3Cl + HCl
Alkanes undergoing nitration
Nitration is the reaction between alkane vapor and conc. HNO3 vapor.
CH4 + HNO3 –> CH3 – NO2 + H2O
alkenes
undergoing hydration
hydration where H from H-OH is attached to the C atom with larger number of H atoms, whereas the OH group from water is attached to the other C atom in the double bond of an alkene.
CH3- CH = CH2 + H-OH –> CH3 – CHOH – CH3
alkenes undergoing polymerization
is another reaction of alkenes where different alkenes are attached together to form a larger molecule. CH2=CH2 + CH2=CH2 + CH2=CH2 –> -CH2-CH2-CH2-CH2-CH2-CH2-
the single unit of CH2=CH2 is called a…. and the product is called a…
single unit is a monomer. product is a polymer
Alkynes also undergo polymerization reactions. When
ethyne is passed through a red hot glass tube, it trimerizes to give benzene.
3 CH= CH –> C6H6
Alkynes undergo halogen addition but yields
2 products due to the presence of 2 pi bonds. Thus ethyne can react with 2 halogen molecules. CH=CH +Cl2 –> CHCl = CHCl
CH= CH + 2Cl2 –> CHCl2 – CHCl2
alkynes undergoing hydrogenation
where addition with H atoms take place in the presence of N, Pd or Pt as catalysts.
CH=CH + H2 –> CH2=CH2 –> CH3- CH3
carbon electron configuration in ground state and excited state
ground state 1s2 2s2 2p2.
excited state 1s2 2s1 2p3
Experimental evidence has shown that the bond angles in methane are not arranged that way but are ….. giving the overall shape of a…
109.5
a tetrahedron
Experimental evidence has also shown that the H-N-H bond angles in ammonia (NH3) are
107 degrees
and the H-O-H bond angles in water are
105 degrees
It is clear from these bond angles that the non-bonding pairs of electrons occupy a reasonable amount of space and are pushing the hydrogen atoms
closer together
. In this model, atoms and pairs of electrons will be arranged to minimize the repulsion of these atoms and pairs of electrons.
VSEPR
The number of these new hybrid orbitals must be equal to the
numbers of
atoms and
non-bonded electron pairs (lone pairs) surrounding the central atom
Criteria for Aromaticity:
1) Pi bonds must lie within cyclic structure.
2) Each atom in the cycle must have p orbital, forming p orbital loop.
3) All p orbitals in the loop must overlap and must be planar.
4) Hückel’s Rule: orbital arrangement must result in a lowering of energy. 4n+2 pi electrons (n is an integer: 0 to 5 usually) in the loop
Hückel’s Rule:
Obital arrangement must result in a lowering of energy. 4n+2 pi electrons (n is an integer: 0 to 5 usually) in the loop
Hydrogenation is what kind of reaction
Addition
Halogenation reaction is what kind
Substitution
Hydration is what kind of reaction
H2O attaches to CH with more bonds
And H goes to the CH with more hydrogen atoms
Nitration is what kind of reaction
Substitution h2O
What reactions have only a single product
Halogentation
Hydrogenation
Cis versus trans
Cis same
Trans different
