BISC 330 Spring 2010 Lecture 4

BISC 330 Spring - BISC 330L Biochemistry Spring Semester 2010 USC Lecture Wednesday 20 January 2010 1 Begin Chapter 2 material… Summary of

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: BISC 330L: Biochemistry Spring Semester 2010 USC Lecture: Wednesday, 20 January 2010 1. Begin Chapter 2 material… Summary of Pauling Method for Estimating ∆ H o In his classic, Nature of the Chemical Bond , Linus Pauling showed for chemical reaction, Reactant(R) Product(P), ∆ H o is related to bond dissocation energies (D A-B ) by ∆ H o = Σ (React. bond D A-B values) - Σ (Prod. bond D A-B values) Comparing D A-B with D A-A and D B-B , he found D A-B = 0.5(D A-A + D B-B ) + ∆ AB = d A + d B + ∆ AB, where ∆ AB is additional bonding energy arising from the electronegativity difference (X A-X B ) , which contributes to bond polarity and stability by increasing attraction between atoms A and B in A-B bond. In a balanced reaction (same atoms on both sides), only the ∆ AB component contributes to ∆ H o . He then showed ∆ A-B (in kcal/mole) = 23|X A-X B | 2 (approx.), so that when equation is balanced (same atoms on both sides) ∆ H o (kcal/mole)= 23{ Σ (R bond |X A-X B | 2 ) - Σ (P bond |X A-X B | 2 )} Major Covalent Bonds in Biochemistry and their Dissociation Energies (D A-B kcal mol-1 )* * L. Pauling. Nature of the Chemical Bond , 3rd Ed., 1960, p.85 H-H 104.2 H-C 98.8 H-N 93.4 H-O 110.6 C-C 83.1 C-H 98.8 C-N 69.7 C-O 84.0 N-N 38.4 N-H 93.4 N-C 69.7 O-O 33.2 O-H 110.6 O-C 84.0 S-S 50.9 S-H 81.1 S-C 62.0 (P-P 51.3) (P-H 76.4) P-O (84.2) Electronegativity values: H 2.1 C 2.5 N 3.0 O 3.5 P 2.1 S 2.5 Example:...
View Full Document

This note was uploaded on 01/30/2010 for the course BISC 330 taught by Professor Petruska during the Spring '08 term at USC.

Page1 / 29

BISC 330 Spring - BISC 330L Biochemistry Spring Semester 2010 USC Lecture Wednesday 20 January 2010 1 Begin Chapter 2 material… Summary of

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online