Transcript Document

KIMIA DASAR
I
APAKAH KIMIA
ORGANIK ?
Ilmu yang mempelajari
senyawa-senyawa hidrokarbon
dan derivatnya
Perbandingan :
7 million senyawa organik
1.5 million senyawa anorganik
SENYAWA ORGANIK
 Materi
tanaman / hewan
 Makanan
 Bahan farmasi/ kosmetik
 Plastik
 Komponen minyak bumi
 Pakaian
Some organic chemicals
Medicines
DNA
•Active Pharmaceutical Ingredients
•Excipients
Fuels
Materials
Essential oils
Pigments
H
I
D
R
O
K
A
R
B
O
N
Senyawa yang terdiri
dari
karbon dan hidrogen
Berdasarkan ikatannya
Hidrokarbon jenuh
Hidrokarbon tak jenuh
alkana, alkena, alkuna, benzena
Carbon (C)
Unsur kehidupan di atas bumi adalah
C
MENGAPA ???
memiliki 4 buah elektron bonding yang
dapat membentuk ikatan kovalen yang
kuat, dapat berupa ikatan tunggal dan
rangkap (2 atau 3)
Molekul organik paling sederhana:
Carbon has 4 valence electrons
Susunan OKTET yang stabil
H
H
H
C
H
H
H
methane
metana
C
H
H
H
Ne
Neon
C
Stable Octet required
Covalent Bonding – Atoms Share Electrons
ALKANA
2
Bentuk dasar
2
C(6) - 1s , 2s ,
1
2px ,
1
2py ,
0
2pz
1
2py ,
1
2pz
Hibridisasi
2
1
1
C(6) - 1s , 2s , 2px ,
Bentuk
tereksitasi
4 sp3
+
2s
+
+
2py
2px
2pz
4 X sp3
Struktur tetrahedral
pada metana
0
109.5
H
C H
H
H
Carbon yang menunjukkan hibridisasi sp3
4 buah ikatan C-H yang ekivalen (ikatan s)
Semua ikatan tunggal dinamakan ikatan s
Alkana
CnH2n+2
consist of only carbon and hydrogen bonded by single covalent bonds single
H
H C H
H
methane
CH3
H H
H C C H
H H
ethane
CH3CH3
H H H H
H C C C C H
H H H H
H H H H H
H C C C C C H
H H H H H
propane
butane
pentane
CH3CH2CH3
CH3CH2CH2CH3
H H H
H C C C H
H H H
Skeletal structure of
only carbon atoms
propane
butane
pentane
CH3CH2CH2CH2CH3
Contoh :
CH 4
4
1
CH3
3
2
CH 2
3
2
1
CH 2
CH 3
4
2-metilbutana
1
6
CH3
2
CH
5
CH3
3
CH
4 2
4
5
CH
CH2
3
2
CH2 CH3
6
CH3
1
3-etil-5-metilheksana
3+5=8
4-etil-2-metilheksana
4+2=6
SIFAT FISIK
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Senyawa non polar, densitas <1, dengan air
membentuk dua lapisan
Larut dalam pelarut organik non polar
Alkana C  4, berbentuk gas, Alkana Mr >, berbentuk
cair, Alkana Mr >>>, berbentuk padat
Semakin besar jumlah atom C, Mr molekul semakin >,
gaya dispersi tiap molekul >, titik didih semakin tinggi
Alkana bercabang td < alkana rantai lurus
padanannya
Ada pengaruh gaya van der Waals antar molekul
Ikatan tunggal mampu berotasi bebas
Melting (blue) and boiling (pink) points
of the first 14 n-alkanes in °C.
Isomers – the have the same molecular formula, but a different
structures
Structural Isomers – same molecular formula, but atoms are bonded
in different orders.
H
H3C
C
CH3
C4H10 – has two isomers, n-butane and isobutane
(2-methylpropane)
CH3
Isobutane
H3C
CH
CH3
CH2
CH3
Has the same molecular
formula as n-pentane, C5H12
Isopentane (2-methylbutane)
CH3
Has different Physical Properties :
m.p,
H3C C CH3
b.p.
CH3
density
Neopentane (2,2-dimethylpropane)
CYCLOALKANES
CnH2n
H2C CH2
C
H2
H2C CH2
H
H
C C H Cyclopropane Bond angles
H
60°
C
H
H
Cyclobutane
Bond angles
88°
Cyclopentane
Bond angles
108°
H2C CH2
Cyclohexane
Bond angles
109.5°
CH3
metilsikloheksana
CH 3
C
CH 3
tert-butilsiklopentana
CH 3
CH 3
1,2-dimetilsikloheksana
CH 3
How to draw Cyclohexane ?
H
H
H
put in axial H’s
H
put in equitorial H’s
H
H
H
H
H
H
H
H
H
H
H
H
H H
H
H
H
H
H H
H
H
REACTIONS OF ALKANES
CH4
+ 2O
Combustion
2
CO2
+ 2 H O + energy
2
Dehydrogenation
RCH2
High Temp.
catalyst
CH2R
RHC
CHR
alkene
+
H
H
Halogenation – radical substitution reactions
light or heat
+ Br2
Br
+ HBr
Halogenation
H
H
H
C
C
H
H
H
+
Heat or Light
or hv
Br2
H
Ethane
C
Heat or Light
or hv
H
H
Methane
+
H
C
C
H
H
Br
+
Bromoethane
H
H
H
Cl2
H
H
C
Cl
+
HCl
H
chloromethane
CH2Cl2 and CHCl3
may be observed
Substitution Reaction – a reaction in which part
of a small reacting molecule replaces an atom or a
group of atoms on the organic molecule
HBr
Alkyl Halides or Haloalkanes
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Naming them
Tend to be Heavier than water
More Toxic than Alkanes
Cl
Cl
C
CH3 CH
Cl
CH
Cl
Cl
Tetrachloromethane
or carbon tetrachloride
CH3
CH3 CH
CH3
CH2 CH2
Br
2-Chloro-3-methylbutane
Cl
3-Bromo-1-chlorobutane
CH2CH3
Br
F
Cl
1-Bromobutane
1-Ethyl-2-fluorocyclohexane
Cl
Cl
C
F
F
Cl
Trichlorofluoromethane
(Freon-11)
Cl
C
Cl
F
F
2-Chloropropane or
Isopropyl chloride
F
F
C
C
F
H
H
Dichlorodifluoromethane
1,1,1, 2-Tetrafluoroethane
(Freon-12)
Chlorofluorocarbons (CFCs)
Refrigerant Gases, Ozone Depletion, More H’s more degradable
X dd+
C
X = F, Cl, Br
X is readily displaced by nucleophiles
Nu Electronegativity is defined as the ability of atoms to attract shared
electrons in a covalennt bond ------------ leads to nucleophilic
substitution in alkyl halides
Cl
Cl C Cl
Cl
Symmetrical molecules have no dipole
moment or have equal distribution of
electrons within covalent bonds
Therefore, they are unreactive!
STEREOCHEMISTRY
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Isomers are different compounds that have the same molecular formula
Structural isomers are isomers that differ because their atoms are
connected in a different order
CH3OCH3 ---- dimethyl ether and
CH3CH2OH ---- ethanol
Stereoisomers differ only in the arrangement of
their atoms in space
Geometric Isomers
Cl
H
Cl
H
C2H2Cl2
Cl
H
cis-1,2-Dichloroethene
H
Cl
trans-1,2-Dichloroethene
Enantiomers are stereoisomers whose molecules are
nonsuperimposable mirror images of one another
Involves a tetrahedral sp3 atom
H
CH3
C
CH2
OH
Chiral Centre
CH3
HO
H
C
CH3
H
C OH
CH2
CH2
CH3
CH3
2-Butanol
CH3
One structure can be superimposed on another
CH3
H C OH
CH3
CH3
HO C H
CH3
If any of the groups
attached to the
tetrahedral atom are
the same, the centre
is achiral.
2-Propanol
The ultimate way to test for
molecular chirality is to construct
models of the molecule and its
mirror image and then determine
whether they are superimposable
Screwdriver is achiral
Socks are achiral
Golf club is chiral
Gloves are chiral
A molecule will not be chiral if it possess a
centre or plane of Symmetry
Properties of Enantiomers
Enantiomers have identical melting points and boiling points
Enantiomers have identical solubilities in solvents
Enantiomers have identical spectra and refractive index
Enantiomers interact, and react with achiral molecules in the
same manner
Enantiomers interact and react with other
chiral molecules at different rates
Enantiomers rotate plane-polarised light by
equal amounts but in opposite directions
Chiral molecules are
optically active
Polarimeter is a devise used to measure the effect of planepolarised light on an optically active compound
No Correlation between the direction of rotation of plane
polarised light and the absolute configuration of a molecule
Clockwise Rotation (+) – dextrorotatory
Anti-Clockwise Rotation (-) – levorotatory
Same Configuration
CH3
H2C
C H
HO
CH2CH3
(R)-(+)-2-Methyl-1-butanol
CH3
H2C
C H
Cl
CH2CH3
(R)-(-)-1-Chloro-2-methylbutanol
An equimolar mixture of two enantiomers is called a Racemic Mixture
It is Optically Inactive
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O
O
H
S-(+)-Carvone
Principle component of
Caraway seed oil and
responsible for the
characteristic odour
H
R-(-)-Carvone
Principle component
of Spearmint oil and
responsible for the
characteristic odour
Receptor Sites in the Nose are Chiral
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