Intermolecular Forces of Attraction.pptx

8/12/2019 Intermolecular Forces of Attraction.pptx

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D O N K I N G E V A N G E L I S T A

P H I L I P P I N E N O R M A L U N I V E R S I T Y - M A N I L A

B S C H E M I S T R Y F O R T E A C H E R S


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OUTLINE OF

DISCUSSION

Two general types of bonds

Intermolecular Bonds

Ion-dipole

Dipole-dipole

Hydrogen bonds

Ion-induced dipole

Dipole-induced dipole Dispersion/London/van der Waals

Biochemical Application and Importance of IMFA


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TWO GENERAL TYPES

OF BONDS

Intramolecular Bonds

Intermolecular Bonds


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INTRAMOLECULAR

BONDS

Reference: Chemistry: The Molecular Nature of Matter and Change, Martin Silberberg


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INTERMOLECULAR

BONDS


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ION-DIPOLE

INTERACTION

When an ion and a nearby polar

molecule (dipole) attract each other, an

ion- dipole force results.

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HYDROGEN

BOND

A special type of dipole-dipole

force arises between molecules

that have an H atom bonded to asmall, highly electronegative

atom with lone electron pairs.


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EXERCISE:

Which among these three molecules will have the possibility

of H-bonding?

A. C2H6

B. CH3OH

C. CH3CONH2


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H-Bonding is very important in

Biological Molecules

especially in the three majorbiopolymersproteins,

nucleic acids and

carbohydrates.


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AMINO ACIDS

Building blocks of proteins.


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Structural Hierarchy of Protein Organization

SEQUENCE STRUCTURE FUNCTION


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ALPHA-HELIX (SECONDARY

STRUCTURE)


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BETA-PLEATED SHEETS

(SECONDARY STRUCTURE)


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TERTIARY STRUCTURE

STABILIZATION


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NUCLEIC

ACIDS


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CARBOHYDRATES

(POLYSACCHARIDES)


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CELLULOSE

(B-1,4-GLUCOSE LINKAGE)


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DIPOLE DIPOLE


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DIPOLE-DIPOLE

FORCES

When polar molecules lie near one

another, as in liquids and solids,

their partial charges act as tiny

electric fields that orient them and

give rise to dipole-dipole forces: the

positive pole of one molecule

attracts the negative pole ofanother.


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For molecular compounds of

approximately the same size

and molar mass, the greater

the dipole moment, the

greater the dipole-dipoleforces between the

molecules are, and so the

more energy it takes to

separate them.


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ION-INDUCED DIPOLE

-An ions charge distorts the

electron cloud of a nearby non-

polar molecule.-Example: Fe(2+) ion in

hemoglobin and O2in the

bloodstream.


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DIPOLE-INDUCED

DIPOLE

-Arise when a polar molecule

distorts the electron cloud of a

nearby non-polar molecule.

LONDON/VAN DER


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LONDON/VAN DER

WAALS/ DISPERSION

FORCES

-Primary responsible for the condensed

states of non-polar substances.

-Caused by momentarily oscillations of

electron charges in the atom, and therefore,

present in all particles.

-Instant dipoles

-The most dominant IMFA.


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Intermolecular Forces of Attraction.pptx