Chapter 1 Chemical Bonding and Chemical Structure

Chapter 1 Chemical Bonding and Chemical Structure

Chapter 7 Cyclic Compounds. Stereochemistry of Reactions Monocyclic Compounds Compounds containing a single ring

Relative stabilities are determined from heats of formation (Hf) All have the same empirical formula: CH2 Thus, stabilities can be readily compared on a per carbon basis 7.1 Relative Stabilities of the Monocyclic Alkanes

2 Cycloalkane Heats of Formation per CH2 7.1 Relative Stabilities of the Monocyclic Alkanes 3

Strain Theory Cycloalkanes encounter three types of strain: Angle Strain Torsional Strain Steric Strain

4 Angle Strain Angle strain: strain due to expansion or compression of bond angles Recall: tetrahedral C likes bond angles of 109.5

5 Torsional Strain Torsional Strain: strain due to eclipsing bonds on neighboring atom Neighboring C-H bonds eclipse each other in

cyclopropane 6 Steric Strain Steric Strain: strain due to repulsive interactions due to atoms that approach each other too closely Occurs between non-bonded atoms

7 Cyclopropane Planar structure Bond angles of 60 Requires that sp3 based bonds are bent

Angle Strain! Bent bonds = weak bonds All C-H bonds are eclipsed Torstional strain! 8

Cyclobutane Less angle strain than cyclopropane More torsional strain larger number of ring hydrogens Slightly bent out of plane One carbon atom is about 25 above Increases angle strain but decreases torsional

strain 9 Cyclopentane Conformations of cyclopentane are nonplanar reduces torsional strain

Planar cyclopentane would have almost no angle strain but very high torsional strain Envelope Four carbon atoms plane The fifth carbon atom is above or below the plane 10

Cyclohexane Adopts a non-planar, puckered conformation Chair conformation Free of angle strain and torsional strain Very stable! Same stability as a typical unbranched alkane

11 Cyclohexane Prevalent in many naturally occurring organic compounds

Menthol Morphine 12 13

The Chair Conformation 14 Drawing Cyclohexane

15 Problems Practice drawing both chair conformations of cyclohexane 16

17 Adding the Hydrogens 18 Conformational Mobility of Cyclohexane

Chair conformations readily interconvert, resulting in the exchange of axial and equatorial positions by a ring-flip 19 20

21 22 Relative Enthalpies

7.2 Conformations of Cyclohexane 23

Recently Viewed Presentations

  • Presentation Title - Boyer & Associates

    Presentation Title - Boyer & Associates

    With the release of Microsoft Dynamics SL 2015 (scheduled for H2 of calendar year 2014), the following Web Apps will be available (including those made available in SL 2011 Web Apps CU1: Project Timesheet Entry - Enter time for a...
  • Race Representations

    Race Representations

    What are the effects of cinematic techniques on character portrayal? How stereotypical are characters and the culture? How does the antagonist reflect the filmmakers' views on the culture overall? How does Disney "voice" the characters in the culture? How does...
  • Paul Klee - Folsom Cordova Unified School District

    Paul Klee - Folsom Cordova Unified School District

    Pop . artists readily made use of commonplace objects, such . as comic strips, packaging, highway signs, and images from film and television. Incorporating the visual noise of their daily lives! A lot of the art centered around different ways...
  • XY Scatter Plots in Excel 2007 - La Salle University

    XY Scatter Plots in Excel 2007 - La Salle University

    Chart with Vertical Gridlines XY Scatter Plots in Excel 2007 Weight versus Position We want to plot weight versus position so we multiply the masses by g=9.8 m/s2. Also when we say weight versus position, we want weight on the...
  • Classical Greece

    Classical Greece

    This time was called the Age of Pericles. He was elected one of the ten generals for 15 consecutive years and so he had more influence than the other strategos. Powerful public speaker and usually persuaded the Assembly to vote...
  • Climate Change - Nuffield Foundation

    Climate Change - Nuffield Foundation

    A Swiss mathematician, Leonhard Euler (1707 to 1783), published the first paper on graph theory in 1736. The paper was based on the Seven Bridges of Konigsberg problem. Residents of Konigsberg wanted to know if it was possible to find...
  • CITY OF LOS ANGELES TARGETED LOCAL HIRE PROGRAM

    CITY OF LOS ANGELES TARGETED LOCAL HIRE PROGRAM

    Older workers protected under the Age Discrimination in Employment Act of 1967 (ADEA) Contact the Personnel Department at [email protected] if you have additional questions about the referral . procedures. The Program welcomes all applicants who have successfully met the requirements...
  • Sample Sales Deck: Managed Services Presentation (Meeting 1)

    Sample Sales Deck: Managed Services Presentation (Meeting 1)

    Managed Services is not only an option, but now a proven one. Dedicated. US-Based Team (not part time, or single threaded). 24/7 team US and in Philippines. Service Desk Manager will be assigned. Most staff on desk can handle Level...