class3_w08

class3_w08 - -Oxidation states of carbon counting owned...

Info iconThis preview shows pages 1–14. 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

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

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

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: -Oxidation states of carbon counting owned electrons provides a means of determining whether a reaction oxidizes or reduces the compound-The C in methane is least oxidized; that in carbon dioxide is most oxidized-Biomass synthesis (carbon cycle) can also be considered a redox reaction Redox reactions in organic molecules In metabolism, carbon compounds are oxidized and reduced stepwise, and the energy is conserved as ATP or used to generate reduced cofactors Rotation about single bonds is possible at low energy cost, because the cylindrical sigma orbitals can maintain overlap The different spatial arrangements of atoms in different rotational orientations are distinct conformations By contrast, rotation about a double bond is very unfavorable energetically because it is necessary to break the pi bond in the rotation Eclipsed conformations are at higher energy. This is called torsional strain . This means that the single-bond rotation is not fully free, but the energy barrier is small (12 kJ/mol; much smaller than covalent bond). The conformers interconvert rapidly at ambient T and the individual conformers cannot be separated. Boat vs. chair conformations of cyclohexane General structure of amino acids Zwitterionic form at pH 7.0 pK a of COO- is about 2.0 pK a of NH 3 + is about 9.5 Example of an amino acid (alanine), where R is CH 3 The central carbon atom is bonded to 4 different substituents This is an example of a chiral center The L and D forms are called stereoisomers They are nonsuperimposable mirror images In nature, the amino acids found in proteins are L Chirality Right/left hands are mirror images that are not superimposable-The chair is achiral; its mirror image is an exactly superimposable copy-Organic molecules are chiral when the central atom is (most commonly) an asymmetric carbon bonded to 4 different substituent groups The chiral molecule and its nonsuperimposable mirror image are enantiomers of each other. Superimposable means that you can pick the molecule up and place it exactly on top of its mirror image by rotating/translating. Note Glycine has no chiral center. Proline is a secondary rather than a primary amine Methionine has a thioether functionality (sulfur) All the side-chain carbons (and S) are sp 3 hybridized Isoleucine has a second chiral center Note that in tryptophan, the lone-pair electrons on the side-chain nitrogen atom are in a p-orbital, so there are 5 (odd #) pairs to satisfy the criterion for aromaticity. Note Serine and threonine side-chains are alcohols The cysteine side-chain is a sulfhydryl group ( p K a = 8) Asparagine and glutamine side-chains are amides Like isoleucine, threonine has a second chiral center Note...
View Full Document

Page1 / 57

class3_w08 - -Oxidation states of carbon counting owned...

This preview shows document pages 1 - 14. Sign up to view the full document.

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