Yhich of the following is not a property of ethers which makes them good solvent
ID: 568793 • Letter: Y
Question
Yhich of the following is not a property of ethers which makes them good solvents in organie reactions A) They dissolve a wide range of polar B) They are nonhydroxylic. C) They have relatively high boiling points for their molecular weights D) They dissolve a wide range of nonpolar E) They are normally unreactive toward strong 2) What two atomic orbitals or hybrid atomic orbitals overlap to form the C-O bond in ethanol? A) C sp2+O sp2 B) C sp3 +O sp3 C) C sp2 + O sp3 D) C sp3+O sp2 E) none of the above Which of the following reagents is the best choice for oxidizing a primary alcohol to an aldehyde? A) H2CrO4 B) LiAlH4 C) Na2Cr207, H2S04 D) KMn04 E) pyridinium chlorochromate 4) When pent-1-ene is treated with mercury(II) acetate in methanol and the resulting product is reacted with NaBH4, what is the primary organic compound which results? A) 3-ethoxypentane D) 2-ethoxypentane 5) In the formation of the following ether, which reaction is preferred and why? B) 1-methoxypentane E) 2-methoxypentane C) 1-ethoxypentane CH CH,OH A) Reaction B is preferred because the oxidation step works best for primary alcohols. B) Reaction A is preferred over reaction B because the smaller methyl iodide would make a better nucleophilic target. C) Reaction A is preferred because the formation of the carbocation would be stabilized in the benzylic position. D) Reaction B would be preferred because lodine is a better leaving group for the SNI reaction. E) There is no difference in these two reactions- they would give approximately the same yields. 6) What are the expected products of the reaction of PhOCH3 with concentrated HI? A) phenol and methanol D) phenol and iodomethane 7) Which of the following is produced by the reaction of (CH3CH2)2S with CH3CH21 A) CH3CH2CH2CH2l B) (CH3CH2)3s+ 1- B) iodobenzene and iodomethane E) none of the above C) iodobenzene and methan C) (CH3CH2)3SExplanation / Answer
1. OPTION A and C. Ethers are functionalized hydrocarbons with C-O-C linkage(s). They thus are quite non-polar and only dissolve a wide range of non-polar compounds rather than polar ones. Possessing C-O-C linkages, they are also devoid of hydroxyl groups. Moreover the carbon oxygen bond gives rise to lower attractive interactions in ethers giving them lower boiling points compared to other hydrocarbons of same emipirical formula as alcohols and to some extent carbonyls have H-bonding which is stronger than the van der Waals forces which exist in ethers.
2. OPTION B. In ethanol there is a carbon-oxygen single bond and no other pi-bonds. Thus one can say that like in methane and other saturated hydrocarbons C has sp3 hybridisation in ethanol. O atom in ethanol is similar to that in water molecule and its hybridisation is sp3 and as it has two more p-electrons than C resulting in two bonding electrons and two lone pairs.
3. OPTION E. Of the given oxidiants, all are very strong oxidising agents with transition metals in high oxidation states all uncontrolled oxidation of alcohols to acids without stopping at the carbonyl stage. Moreover, primary alcohols are quite reactive towards oxidation and readily get converted into acids with carbonyls only as intermediates. PCC however is only a mild oxidant as the pyridinium ion is not so acidic thus giving only a controlled oxidation resulting in conversion of primary alcohols to aldehyde alone and not all the way to acids,
4. OPTION E. Reaction of alkenes with mercuric acetate in alcohols proceed through a three-membered mercury-bridged intermediate whose regioselectivity proceeds through Markonikov's rule giving the most substituted carbon open for attack as it forms the most stable carbocation. Here out of the first and second carbons of pent-1-ene, the second carbon, being a secondary carbon is more stable than the first which is a primary carbon as the former has more hyperconjugation. Thus the attack of methoxide ion formed in the reaction occurs at the second carbon giving 2-methoxypentane upon final treatment with sodium borohydride which reduces the mercury-bridged intermediate to give the final product.
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