2 chem mc (organic chem)

[匿名]

2012-02-12 3:48 am

1.oxidation of an alkene X gives a diol. Further oxidation gives a dioketone.
What could X be?
A. (CH3)2C=C(CH3)2
B.CH3CH=C(CH3)2
C.C6H5CH=CHC6H5
D. (C6H5)C=CHCH3

2. menthol shown below is used in skin lotions.

圖片參考：http://imgcld.yimg.com/8/n/HA08059003/o/701202110080313873436220.jpg

which of the following statements concerning menthol is /are correct?
1.menthol has 2 chiral carbons
2. menthol can be dehydrated by heating with conc. H2SO4
3. when warmed with K2Cr2O7/H+ solution, menthol turns the orange dichromate solution to green.
A. 1 only
B. 2 only
C 1 and 3 only
D. 2 and 3 only

回答 (1)

不用客氣

2012-02-12 8:38 am

✔ 最佳答案

1.
The answer is : C. C6H5CH=CHC6H5

To be further oxidized to a diketone from the diol formed, each of the bondingatoms of the C=C double bond should at least be bonded to at least one H atom,i.e.
-CH=CH- + [O] + H2O → -CH(OH)-CH(OH)-
-CH(OH)-CH(OH)- + 2[O] → -CO-CO- + 2H2O

A. Both the bonding atoms of the C=C double bond are NOT bonded to any H atom.
B. The right bonding atom of the C=C double bond is NOT bonded to any H atom.
C. Each of the bonding atoms of the C=C double bond is bonded to one H atom.
D. The left bonding atom of the C=C double bond is NOT bonded to any H atom.

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2.
The answer is : D. 2 and 3 only

1. incorrect
Menthol has 3 chiral carbons : the C atom bonded with the -CH(CH3)2group, that bonded to the -OH group, and that bonded to the -CH3group.

2. correct
-CH(OH)-CH< can be dehydrated to -CH=C<.

3. correct
-CH(OH)- can be oxidized to -CO- by K2Cr2O7/H⁺ solution, and the orange dichromate ions arereduced to green chromium(III) ions.

參考: micatkie

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