[Donald A. McQuarrie, John D. Simon] Physical Chem(BookZZ.org)
1279 pág.

[Donald A. McQuarrie, John D. Simon] Physical Chem(BookZZ.org)


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u a t i o n s , a l l o f w h i c h , i t a p p e a r e d , h a d t o b e c o m m i t t e d t o m e m o r y a n d 
r e p r o d u c e d i n e x a c t l y t h e s a m e f o r m i n s u b s e q u e n t e x a m i n a t i o n s . N o t o n l y d i d 
t h e s e e q u a t i o n s c o n t a i n a l l t h e n o r m a l a l g e b r a i c s y m b o l s b u t i n a d d i t i o n t h e y 
w e r e l i b e r a l l y s p r i n k l e d w i t h s t a r s , d a g g e r s , a n d c i r c l e s s o a s t o s t r e t c h e v e n 
t h e m o s t p o w e r f u l o f m i n d s . F e w w o u l d w i s h t o d e n y t h e m i n d - i m p r o v i n g a n d 
i n d e e d c h a r a c t e r - b u i l d i n g q u a l i t i e s o f s u c h a s u b j e c t ! H o w e v e r , m a n y y o u n g 
c h e m i s t s h a v e m o r e u r g e n t p r e s s u r e s o n t h e i r t i m e . " 
W e c e r t a i n l y a g r e e w i t h t h i s l a s t s e n t e n c e o f P r o f e s s o r S m i t h ' s . T h e f a c t i s , h o w e v e r , 
t h a t e v e r y y e a r t h o u s a n d s u p o n t h o u s a n d s o f s t u d e n t s t a k e a n d p a s s p h y s i c a l c h e m i s t r y , 
a n d m a n y o f t h e m r e a l l y e n j o y i t . Y o u m a y b e t a k i n g i t o n l y b e c a u s e i t i s r e q u i r e d 
b y y o u r m a j o r , b u t y o u s h o u l d b e a w a r e t h a t m a n y r e c e n t d e v e l o p m e n t s i n p h y s i c a l 
c h e m i s t r y a r e h a v i n g a m a j o r i m p a c t i n a l l t h e a r e a s o f s c i e n c e t h a t a r e c o n c e r n e d w i t h 
t h e b e h a v i o r o f m o l e c u l e s . F o r e x a m p l e , i n b i o p h y s i c a l c h e m i s t r y , t h e a p p l i c a t i o n o f 
b o t h e x p e r i m e n t a l a n d t h e o r e t i c a l a s p e c t s o f p h y s i c a l c h e m i s t r y t o b i o l o g i c a l p r o b l e m s 
h a s g r e a t l y a d v a n c e d o u r u n d e r s t a n d i n g o f t h e s t r u c t u r e a n d r e a c t i v i t y o f p r o t e i n s a n d 
n u c l e i c a c i d s . T h e d e s i g n o f p h a r m a c e u t i c a l d r u g s , w h i c h h a s s e e n g r e a t a d v a n c e s i n 
r e c e n t y e a r s , i s a d i r e c t p r o d u c t o f p h y s i c a l c h e m i c a l r e s e a r c h . 
T r a d i t i o n a l l y , t h e r e a r e t h r e e p r i n c i p a l a r e a s o f p h y s i c a l c h e m i s t r y : t h e r m o d y n a m -
i c s ( w h i c h c o n c e r n s t h e e n e r g e t i c s o f c h e m i c a l r e a c t i o n s ) , q u a n t u m c h e m i s t r y ( w h i c h 
c o n c e r n s t h e s t r u c t u r e s o f m o l e c u l e s ) , a n d c h e m i c a l kinetic~ ( w h i c h c o n c e r n s t h e r a t e s X V I I 
xviii PHYSICAL CHEMISTRY 
of chemical reactions). Many physical chemistry courses begin with a study of ther-
modynamics, then discuss quantum chemistry, and treat chemical kinetics last. This 
order is a reflection of the historic development of the field. Today, however, physical 
chemistry is based on quantum mechanics, and so we begin our studies with this topic. 
We first discuss the underlying principles of quantum mechanics and then show how 
they can be applied to a number of model systems. Many of the rules you have learned 
in general chemistry and organic chemistry are a natural result of the quantum theory. 
In organic chemistry, for example, you learned to assign molecular structures using 
infrared spectra and nuclear magnetic resonance spectra, and in Chapters 13 and 14 
we explain how these spectra are governed by the quantum-mechanical properties of 
molecules. 
Your education in chemistry has trained you to think in terms of molecules and 
their interactions, and we believe that a course in physical chemistry should reflect 
this viewpoint. The focus of modem physical chemistry is on the molecule. Cur-
rent experimental research in physical chemistry uses equipment such as molecular 
beam machines to study the molecular details of gas-phase chemical reactions, high 
vacuum machines to study the structure and reactivity of molecules on solid inter-
faces, lasers to determine the structures of individual molecules and the dynamics 
of chemical reactions, and nuclear magnetic resonance spectrometers to learn about 
the structure and dynamics of molecules. Modem theoretical research in physical 
chemistry uses the tools of classical mechanics, quantum mechanics, and statistical 
mechanics along with computers to develop a detailed understanding of chemical 
phenomena in terms of the structure and dynamics of the molecules involved. For 
example, computer calculations of the electronic structure of molecules are providing 
fundamental insights into chemical bonding and computer simulations of the dynamical 
interaction between molecules and proteins are being used to understand how proteins 
function. 
In general chemistry, you learned about the three laws of thermodynamics and 
were introduced to the quantities, enthalpy, entropy, and the Gibbs energy (formerly 
called the free energy). Thermodynamics is used to describe macroscopic chemical 
systems. Armed with the tools of quantum mechanics, you shall learn that thermody-
namics can be formulated in terms of the properties of the atoms and molecules that 
make up macroscopic chemical systems. Statistical thermodynamics provides a way 
to describe thermodynamics at a molecular level. You shall see that the three laws of 
thermodynamics can be explained simply and beautifully in molecular terms. We be-
lieve that a modem introduction to physical chemistry should, from the outset, develop 
the field of thermodynamics from a molecular viewpoint. 
Our treatment of chemical kinetics, which constitutes the last five chapters, devel-
ops an understanding of chemical reactions from a molecular viewpoint. For example, 
we have devoted more than half of the chapter of gas-phase reactions (Chapter 28) to the 
reaction between a fluorine atom and a hydrogen molecule to form a hydrogen fluoride 
molecule and a hydrogen atom. Through our study of this seemingly simple reaction, 
many of the general molecular concepts of chemical reactivity are revealed. Again, 
quantum chemistry provides the necessary tools to develop a molecular understanding 
of the rates and dynamics of chemical reactions. 
P r e f a c e 
P e r h a p s t h e m o s t i n t i m i d a t i n g a s p e c t o f p h y s i c a l c h e m i s t r y i s t h e l i b e r a l u s e o f 
m a t h e m a t i c a l t o p i c s t h a t y o u m a y h a v e f o r g o t t e n o r n e v e r l e a r n e d . A s p h y s i c i s t s s a y 
a b o u t p h y s i c s , p h y s i c a l c h e m i s t r y i s d i f f i c u l t w i t h m a t h e m a t i c s ; i m p o s s i b l e w i t h o u t i t . 
Y o u m a y n o t h a v e t a k e n a m a t h c o u r s e r e c e n t l y , a n d y o u r u n d e r s t a n d i n g o f t o p i c s s u c h 
a s d e t e r m i n a n t s , v e c t o r s , s e r i e s e x p a n s i o n s , a n d p r o b a b i l i t y m a y s e e m a b i t f u z z y a t 
t h i s t i m e . I n o u r y e a r s o f t e a c h i n g p h y s i c a l c h e m i s t r y , w e h a v e o f t e n f o u n d i t h e l p f u l t o 
r e v i e w m a t h e m a t i c a l t o p i c s b e f o r e u s i n g t h e m t o d e v e l o p t h e p h y s i c a l c h e m i c a l t o p i c s . 
C o n s e q u e n t l y , w e h a v e i n c l u d e d a s e r i e s o f t e n c o n c i s e r e v i e w s o f m a t h e m a t i c a l t o p i c s . 
W e r e a l i z e t h a t n o t