Chemistry 2000 (Fall 2008) Problem Set #7 Organic by cru50699


									                                      Chemistry 2000 (Fall 2008)
                        Problem Set #7: Organic Chemistry – Shapes and Names

   Answers to Questions in Petrucci (only those w/out answers at the back of the book)
   26.44 Alkenes contain carbon-carbon double bonds which have π bonds as well as σ bonds.
         Cycloalkanes only have σ bonds. Since π bonds are usually weaker than σ bonds, alkenes
         tend to be more reactive than cycloalkanes.

   (a)            Cl                H                          (b)        H             Cl
                        C       C                                             C     C
                 Cl                                                    H              CH3
                 H3 C           H                                      H3C          CH3

   Additional Practice Problems
   1.     In each of the following sets of molecules, circle all of the molecules which are isomers of
          each other:
                O                                                       O                      O


                                                             H3C C C        O                                              O
                                                                                  C C        C    CH3
                                                                                  H2                                           O

   2.          The penicillins are a series of antibiotics containing the same core structure (shown in blue):
(aromatic                                                         phenol*
                                                                            HO                                amine
ring)                                                                                                   NH2
                            O                   H                                                    *        H
                  ether                                      thioether*                                                    thioether*
                                            N                                                             N
                             O                  * * S                                              O          * * S
                            amide                   N                                            amide            N
                                        O                *        carboxylic acid                       O              *
                                    amide                     O                                     amide                  O
              penicillin V                          HO                      amoxycillin                           HO
                                                                                                              carboxylic acid

             *We would accept this labeled as an arene (aromatic ring) and an alcohol.
             *You do not need to have labeled the thioether group (“thio” = sulfur)
(a)   Draw the structure of an aldehyde with a molecular formula of C3H6O.                                                          H       H
                                                                                                                     H                  C           H
                                                                                                                                C               C
                                                                                                                         H          H           O
(b)   Draw an isomer of this aldehyde that is an alcohol.
      Any of:    H                       OH                                                     H                                       H       H

          H       C               OH           H           C               H           HO       C               H                           C
                                                                                                                             H                          OH
              C           C                            C           C                        C           C                               C       C
              H       H       H                        H       H       H                    H       H       H                       H               H
      (FYI: It is not usual to see –OH attached to a carbon involved in one or more π bonds.)
(c)   Draw an isomer of this aldehyde that is an ether.
      Any of:                                           H
                              H        H       H                                                                            H           H
                                                                               O   C    H                           O
                  H           C            C                                                            H                       C
                      C            O               H                                                            C       C               H
                                                                   H           C   C    H
                      H                                                                                     H               H
                                                                               H   H

(d)   Draw an isomer of this aldehyde that is a ketone.                                                             O

                                                                                                        H            C                  H
                                                                                                                C            C
                                                                                                            H       H H             H

4.    Draw all of the structural isomers for each of the formulas below. (For brevity, only one
      stereoisomer for each answer is shown. If you drew cis instead of trans, it’s still right.)
(a)                                                                              Br
              Br             Cl                                                                   Cl                                                         Br
                                                Cl             Br

5.    Name each of the following molecules according to IUPAC rules:
(a)            I                  (b)                        (c)                           3
                                                    6       1
                      2                         5
              1               3                                                        2       1
             7                4
                                                    3       2
                  6       5

(d)    4     3                        (e)                               (f)        OH
                      F                                 1
                                                                    O                              4
                                            6                                                                  6
                 2        1       H                             2             1    2                   5
                                            5                   3
                      O                                 4

(a)   1,3-diethyl-2-iodo-5,6-dimethylcycloheptane
(b)   1,2,3,3,6,6-hexamethylcyclohexene
(c)   2-bromo-1,1-dipropylcyclopropane
(d)   2-fluoro-2-methyl-3-butenal
(e)   2-methoxy-1-methyl-4-propylbenzene
(f)   trans-5,5-dimethyl-3-hexen-2-ol

6.    For each of the following incorrect names:
      (i)    Draw the molecule described by the name.
      (ii)   Give the correct IUPAC name for the molecule drawn.
(a)   3-chloro-2-propylpropane

      Should be: 1-chloro-2-methylpentane
      (wrong main chain; pentane is longer than propane)                               Cl

(b)   trans-1,1-dimethyl-2-chloro-3-iodocyclobutane                                                                I
                                                                                       H3C                 H
      Should be: trans-2-chloro-3-iodo-1,1-dimethylcyclobutane
      (substituents not in alphabetical order)                                                                     H
                                                                                       H3C                 Cl
(c)   1-hexyne-3,6-diol
      Should be: 5-hexyne-1,4-diol                                                 C
      (main chain numbered from wrong end; make first alcohol 1 not 3)                                                 OH
7.    Indicate whether each of the following pairs of molecules is (A) a pair of enantiomers, (B)
      two different views of the same molecule or (C) neither:
(a)              OH                                    OH
                               and                                       enantiomers

(b)              OH                            OH
                               and                                       enantiomers

(c)             OH
                               and                  OH

(d)             OH
                                                  OH                     enantiomers

8.    Circle all of the chiral centres in the molecules in question 7.
              see red circles above

9.    One of the molecules in question 7 is not chiral. Draw this achiral molecule and explain
      why it is not chiral.
              The molecule at the right is not chiral because it has
              a plane of symmetry (shown in red on top-view).                     =
              As such, it is superimposable with its mirror image.         OH
                                                                         OH          HO OH

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