Ella Li's List: 2ed exam for the 109H chemistry class

• Note that the hydrogen bonds holding together the two peptide chains are not  180 degrees
• • A question relates to this diagram in the practice exam. The side chain reaction is between O H

  • he interaction is between H from -N-H and O from -C=O
    one line is parallel and one line is antiparallel
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• the interaction is between H from -N-H and O from -C=O
  one line is parallel and one line is antiparallel - Ella Li on 2008-10-19

• • I just curious about the alfa helix interaction. I found this rally nice pic since I thought this might on the exam. This relate to our lab question and it's also relate to our review exam. it;s always NH and C=O interat with each other and from hydrogen bond. There is no interaction occurs between R group or C in the mainchain.
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• Secondary structure - this term refers to the arrangement of amino acids that  are close together in a chain. Examples of secondary structures are  helices and pleated sheets. An alpha helix is a tightly  coiled, rodlike structure which has an average of 3.6 amino acids per turn. The  helix is stabilized by hydrogen bonding between the backbone carbonyl of one  amino acid and the backbone NH of the amino acid four residues away. All main  chain amino and carboxyl groups are hydrogen bonded, and the R groups stick out  from the structure in a spiral arrangement. As seen in the table below, there  are several types of alpha helix that arise from the degree of hydrogen bonding  in the helix.
• • beta barral-in our lab, we did a question about this.
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• The interior of a protein molecule contains a preponderance of hydrophobic  amino acids, which tend to cluster and exclude water. The core is stabilized  by Van der Waals forces and hydrophobic bonding.

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• Ester
  
  .......O
  ........||
  R----C----O----R'
• Aldehyde
  
  R----C===O
  .........|
  ........H
  
  Ketone
  
  R----C===O
  .........|
  ........R'
• Carboxylic Acid
  
  R----C===O
  .........|
  ........OH
• R----C===O
  .........|
  

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• • primary alcholol's oxidation form aldehyde
    secondary alcholol's oxidation form ketone
• relationship between the primary alcohol and the aldehyde formed.
• • aldehyde's oxidation forms carboxylic acids
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• Secondary alcohols are oxidised to ketones
• Tertiary alcohols aren't oxidised by acidified sodium or potassium  dichromate(VI) solution. There is no reaction whatsoever.

  • Tertiary alcohol is much harder to oxidize and it doesn't react with potassium dichromate
    this answer the review question
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• • this is our in class experiment

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• The reaction of aldehydes and ketones with ammonia or 1º-amines forms  imine derivatives, also known as Schiff bases, (compounds having a  C=N function). This reaction plays an important role in the synthesis of  2º-amines, as discussed earlier. Water is  eliminated in the reaction, which is acid-catalyzed and reversible in the same  sense as acetal formation.

   R₂C=O   +   R'NH₂      R'NH–(R₂)C–O–H       R₂C=NR'   +   H₂O

  • the ketone or aldehyde reaction with NH2