问题 填空题

A和B两种物质的分子式都是C7H8O,它们都能跟金属钠反应放出氢气。A不溶于NaOH溶液,而B能溶于NaOH溶液,B能使适量溴水褪色,并产生白色沉淀,A不能。B的一溴代物有两种结构,写出A和B的结构简式________________和名称_________________。

答案

A是苯甲醇:是对甲基苯酚:

从分子式C7H8O看,只能知道A和B不是饱和化合物,但结合具体性质联系起来综合考虑就可以推断出A和B。由于A和B都能与金属钠反应放出氢气,且这两种物质中每个分子都只含有一个氧原子,所以它们的结构中有羟基,即它们为醇和酚。

A不溶于NaOH溶液,说明A为醇,A不能使溴水褪色,则A中一定含有苯环,推测A只能是一种芳香醇——苯甲醇。B能使溴水褪色,并生成白色沉淀,进一步证明它是酚类——甲基苯酚。但甲基苯酚有邻、间、对三种同分异构体,其中对甲基苯酚的一溴代物含有两种结构。

单项选择题

Home prices slid in November, raising questions about whether the housing recovery is robust enough to maintain a sustained turnaround. From October to November, home prices fell 0.2% after (1) 0.1% in October, according to a report Tuesday by Standard & Poor’s/Case-Shiller’s home price index. (2) five of the 20 metro areas (3) by the index saw price increases for the month.

On a(n) (4) basis, prices were 5.3% lower in November than in November 2008. Prices were the same as in late 2003. "What we’ve seen (5) the past couple of months is that the pace of (6) has fallen down," says Maureen Maitland of Standard & Poor’s. "Some markets have (7) Is that because we haven’t (8) the foreclosure (回赎权的取消) cycle Because of unemployment We’re not seeing the (9) we were seeing in the last summer months. "

Metro areas that have seen a retreat in home prices (10) Seattle, Charlotte, Las Vegas and Tampa. All four (11) gains they made in recent months (12) . (13) , for the 20-metro index, the annual rate of decline is improving. That (14) , with other recent housing reports that show prices (15) or accelerating, could point to (16) the housing market is starting to (17) its footing, some economists say. Existing home sale prices were $178 300 in December, which is 1.5% higher than December 2008, according to a report this week by the National Association of Realtors. That was the first year-over-year (18) in median price since August 2007.

"The most (19) thing we can say is not only the market is stabilizing, but we’ve seen that housing demand is p," says Bernard Baumohl, with the Economic Outlook Group. "Housing probably will continue to climb upwards through the summer, (20) it could slip a little as the tax credit expires. \

19()

A.expanding

B.continuing

C.puzzling

D.encouraging

判断题