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Organic Chemistr yOrganic Chemistr y

Laboratorium Kimia Organik Jurusan KimiaLaboratorium Kimia Organik Jurusan Kimia Fakultas Matematikan dan Ilmu Pengetahuan Alam Fakultas Matematikan dan Ilmu Pengetahuan Alam

Unive rs it as Pad jadj ar an Uni ve rs it as Pad jadj ar an20092009

. , .Dr Dikdik Kurnia M Sc. , .Dr Dikdik Kurnia M Sc

Molecular Compounds (Covalent Bond)Molecular Compounds (Covalent Bond)


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Molecular Compounds (CovalentMolecular Compounds (CovalentBond)Bond)

The shape of molecules is essent ial to to its,propert ies especial ly to i ts interaction wth l iving

.system Ionic compounds -are hight melt ing crystall ine sol ids

.composed of posi t ively and negat ively charged ions,What kind of chemical compounds can be gasses

, -l iquids or low melt ing sol ids at room temperature?

Searching for the smallest particles of most suchmaterials leads not to atoms or ions but to molecules A group of atomsconnected to each other by thesecon major type of chemical bond, the covalent bond.


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.1 What is covalent bond? B e a b l e t o d e f i n e t h e c o v a l e n t b o n d a n d

d e s c r i b e i t s i n f o r m a t i o n ..2 How does the octet rule apply to covalent bond

formation? B e a b l e t o p r e d i c t t h e n u m b e r s o f c o v a l e n t b o n d

-u s u a l l y f o r m e d b y t h e m o r e c o m m o n m a i n g r o u p

e l e m e n t s ..3 How are molecul ar compounds represented by

formulas? B e a b l e t o ,i n t e r p r e t m o l e c u l a r f o r m u l a s

,s t r u c t u r a l f o r m u l a s a n d L e w i s s t r u c t u r e s ..4 How are elecrons arranged in covalent bonds?

B e a b l e t o ,r e c o g n i z e t h e o c c u r r e n c e o f s i n g l e, .d o u b l e a n d t r i p l e c o v a l e n t b o n d s

.5 ,How are electron pairs arranged in molecules and what is their influence on molecular shape?

B e a b l e t o d r a w L e w i s s t r u c t u r e s a n d u s e t h e m t op r e d i c t m o l e c u l a r g e o m e t r y .


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, -O rg an ic C he m is tr y P ha rm ac y.2 0 0 9 0 1 o f 5 0

.6 When are bonds and molecules polar? B e a b l e t o u s e e l e c t r o n e g a t i v i t y a n d m o l e c u l a r

g e o m e t r y t o p r e d i c t b o n d a n d m o l e c u l a r p o l a r i t y .

7. When are the major differences in propertiesbetween ionic and molecular compounds ?

B e a b l e t o c o m p a r e t h e s t r u c t u r e s ,

c o m p o s i t i o n s , a n d m e l t i n g p o i n t s o f i o n i c a n dm o l e c u l a r c o m p o u n d s .8. Under what circumstances are molecular

compounds converted to ions ? B e a b l e t o d e s c r i b e i o n f o r m a t i o n b y h y d r o g e n

l o s s o r a d d i t i o n .



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Covalent BondCovalent BondMolecules , a group of atoms held together by covalentbonds in a discrete unit that is capable ofindependent existane.

Covalent bond , a bond that results when two atomsshare one more pairs of electron.Diatomic molecules , molecule that consists of twoatoms bonded together


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Covalent BondCovalent Bond


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When two singly occupied p orbitals overlap , theelectron density becomes concentrated in the

region between the atoms, joining them togetherby a single covalent bond.

Overlap of p orbitals.


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The stable bond is formed at the point where theenergy is at minimum. The bond length is the distance

between nuclei in a stable bond, and the bond energyis the amount of energy that must be supplied to break

C h a n g e i n p o t e n t i a l e n e r g y a s t w oa p p r o a c h i n g a t o m s f o r m a c o v a l e n tb o n d .


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Covalent Bonding, The Octet Rule, and TheCovalent Bonding, The Octet Rule, and ThePeriodic TablePeriodic Table

Covalent bonds can form between unlike atoms as welllas between like atoms, and molecular compounds arecomposed of atoms of two or more elements (a chemicalcompound composed of molecules).

Hydrogen bondsto 1 hydrogen

atom


atom


atom


atom

H2 H2O NH3 CH4

Biomolecule, a molecules of a compound that occursnaturally and plays a role in the chemistry of l ivingthings


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Covalent Bonding, The Octet Rule, and TheCovalent Bonding, The Octet Rule, and ThePeriodic TablePeriodic Table

Biomolecule, a molecules of a compound that occursnaturally and plays a role in the chemistry of l iving

things


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Multiple Covalent BondsMultiple Covalent Bonds

The bonding in some molecules cannot be explained bythe sharing of one electron pair in single covalentbonds like the Cl Cl bond in Cl 2 and O H bonds in H 2O.

For example, the carbon and oxygen atoms in carbondioxide, CO 2, and the nitrogen atoms in the N 2molecule

could not have electron octets if only single bondswere present:


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Multiple Covalent BondsMultiple Covalent Bonds

Single covalent bond , a covalent bond that results fromsharing of two electrons between atoms.

Double covalent bond , a covalent bond that results fromsharing of two electron pairs between atoms.

Single covalent bond , a covalent bond that results fromsharing of three electron pairs between atoms.


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Structural FormulasStructural Formulas Molecular Formula, a formula that shows by subscripts

the numbers and kinds of atoms in one molecules.

Structural Formula, a formula that shows how atomsare connected to each other.

Lone pair, a pair of outer-shell electrons not usedby an atom for forming bonds


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Structural FormulasStructural Formulas

In ionic compounds,the smallestparticles areions.

In molecularcompounds, thesmallestparticles are

molecules.Distinction between ionic andmolecular compounds


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Coordinate Covalent BondsCoordinate Covalent Bonds

In the covalent bonds, each electron in the shared

pairs is from adifferent atom

In the coordinate covalent bonds , both electrons aredonated from same atom to form the bonds.


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Coordinate Covalent BondsCoordinate Covalent Bonds

Reactant molecules held in place by coordination to

Zn2+ ion in an enzym


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Drawing Lewis StructuresDrawing Lewis Str uctures3. Place lone pairs so that, except for hydrogen,

each non-metal atom connected to the central atom hasan octet

4. Place any remaining electrons on the central atom.Thus far, have used 24 of the 26 available

electrons-6 electrons in three single bonds and 18electrons in the three lone pairs on each chlorineatom. This leaves two electrons for one lone pair onphosphorus.

4. Check to see that each atom has an electron octetor other correct number of valence electrons and thatall avalable electrons have been used. If not, useone or more lone pairs to form multiple bonds toatoms that can have them.

In the structure above, each atom has an octet andall 26 available electrons have been used The

P

Cl

ClCl

... . . .

..

.. ..

..

. . . .

P

Cl

ClCl

..

. . . ...

.. ..

..

. . . .. .


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Drawing Lewis StructuresDrawing Lewis Str uctures

Structural Formula Based on Common Bonding Pattern of H,C, O, N, and X (Halogen) Atoms.In many molecules, especially the organic molecules ofgreatest interest in later chapters, hydrogen, carbon,oxygen, nitrogen, and halogen atoms can be expected tohave the following common bonding patters: C atoms are often bonded to each other. C atoms form four covalent bonds (and has no lonepairs in neutral molecules). N forms three covalent bonds and has one lone pair. O forms two covalent bonds and has two lone pairs. H forms one covalent bonds. Halogen atom (X = F, Cl, Br, I) forms one covalent bond

and have three lone pairs.Condensed structure, a structure inwhih central atoms and the atoms bond edto them are written as groups


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The Shapes of MoleculesThe Shapes of Molecules

Molecular shapes can be predicted by analyzing a Lewisstructure in the following way:

The atom for which the bonding geometry is of interest .I n a s i m p e m o l e c u l e l i k e P C l 3 o r C O 2 t h i s u s u a l l y t h ec e n t r a l a t o m .

C o u n t t h e n u m b e r o f e l e c t r o n - c h a r g e c l o u d s s o u r r o n d i n gt h e a t o m o f i n t e r e s t i n t h e L e w i s s t r u c t u r e . T h e n u m b e ro f c h a r g e c l o u d s i s s i m p l y t h e t o t a l n u m b e r o f b o n d sa n d l o n e p a i r s . M u l t i p l e b o n d s c o u n t t h e s a m e a s s i n g l eb o n d s , b e c a u s e w e r e i n t e r e s t e d o n l y i n t h e n u m b e r o f

c h a r g e c l o u d s , n o t i n h o w m a n y e l e c t r o n s t h e r e a r e i ne a c h c l o u d .

D e t e r m i n e t h e m o l e c u l a r s h a p e a c c o r d i n g t o t h e n u m b e r o fe l e c t r o n - c h a r g e c l o u d s , t a k i n g i n t o a c c o u n t t h e e f f e c t

o f l o n e p a i r s o n m o l e c u l a r s h a p e . T h e p o s s i b l em o l e c u l a r s h a p e s a r e s u m m a r i z e d i n Ta b l e . 6 . 2 . F o r


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Electron-pair charge cloudssurrounding a bonded atom.

The drawings show the arrangments

of two, three, and four chargeclouds at maximum distance fromeach other.

The charge clouds may be fromsingle, double, or triple bonds, orlone pairs.


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Bond angle, the angle formedbetween any two adjacentcovalent bonds.

Tetrahedron, a geometricalfigure with four identical


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The central atom is located at the ce nter of thetetrahedron, and the four outer-shell electron pairs areoriented toward the corners.

The bond angle be tween any two pai rs i s, ideal ly, 109.5 .

Tetrahedral molecular geometry.

The molecular geometry of water, ammonia, methane, and manyother molecules is based on the tetrahedron


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Bond angle, the angle formed between any two adjacentcovalent bonds.

Tetrahedron, a geometrical figure with four identicaltriangular faces


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Electronegativity and Bond TypeElectronegativity and Bond Type


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Electronegativity and Bond TypeElectronegativity and Bond Type

Electronegativity, the ability of an a tom in a molecule toattract electron; a numerical value on the electronegativityscale

Polar covalent bond, a covalent bond inwhich one atomattracts bonding electrons more strongly than other atom.


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Polar MoleculesPolar MoleculesPolar covalent bond, a covalent bond inwhich one atomattracts bonding electrons more strongly than other atom.

Naming Binar y MolecularNaming Binar y Molecular


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Naming Binar y MolecularNaming Binar y MolecularCompoundsCompounds

1.Name the first element in the formula

with the element name, plus a prefixif needed.2.Name the second element in the

formula with element name modifiedwith-ide (as for ionc compound), plusa prefix if needed.

Propert ies of MolecularPropert ies of Molecular


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Propert ies of MolecularPropert ies of MolecularCompoundsCompounds

Interaction forces, forces of attraction and repulsionbetween partial charges in different molecules

I F M l l C dI F M l l C d


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Ions From Molecular CompoundsIons From Molecula r Compounds(An Introduction to Acids and Bases)(An Introduction to Acids and Bases)

Acid, a subsance that is able to donateahydrogen ion, H +

I F M l l C dI F M l l C d


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Ions From Molecular CompoundsIons From Molecula r Compounds(An Introduction to Acids and Bases)(An Introduction to Acids and Bases)

Acid, a subsance that is able to donateahydrogen ion, H +


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