一道很简单的化学问题。Organic Chemistry

無聊人

这是一道历届考题。

The structure of three compounds P, Q and R are shown.



Which compounds are isomers of each other?

A  P and Q only
B  P and R only
C  Q and R only
D  P, Q and R                                        (N2001  P1  34)

sonuvdabitch

P 和Q?????????????????????

(^.^)

C  Q and R only

雨天之魂

说起 isomer 的话, 三个都是 isomer..因为同样是 三个 C, 一个 O, 八个 H.

Definition of Isomer: Organic compounds that have the same molecular formula but different arrangements of atoms.

嗯，　坛主抱歉一下哦．．我从课本引用原文．．

Ｑ　跟 R 是 position isomer...　同样是　-OH group, 一个在第一个　C, 一个在第二个　C．
Ｐ　跟其他两个比较的话是 functional group isomer, 它是一个 ether.. -O- group.

所以答案是 D, 三个都是 isomer.

楼主，　你自己都说是简单的题目了，你应该知道答案了吧？

無聊人

答案是D。

楼上的，你的definition是对的。

無聊人 于 3-9-2004 06:57 PM  说 :
答案是D。

楼上的，你的definition是对的。

当然是D。呃，坛主的CHEMISTRY是瞒不赖的哦！

[订正]答案是P，Q和R。

Isomers are defined as compounds that have the same molecular formula, but different structures. There are two ways in which isomers can differ. When they differ in the way the atoms are connected, they are called constitutional isomers. Butane and isobutane, for example, are constitutional isomers.

Constitutional isomers have similar chemical properties but different physical properties. Butane melts at -138.4C and boils at -0.5C, whereas isobutane melts at -159.6C and boils at -11.7C .

Isomers in which the atoms are connected in the same way, but differ in the way the atoms are arranged in space are called stereoisomers. Thus, as noted in the previous section, cis/trans isomers such as cis- and trans-2-butene are stereoisomers.

Cis/trans isomers also have similar chemical properties but different physical properties. Cis-2-Butene, for example, freezes at -138.9C, whereas trans-2-butene freezes at -105.6C.

[ Last edited by passerby on 25-11-2004 at 08:03 PM ]

雨天之魂

嗯? 还没完哦?

passerby, ... 你自己不也说了...
第一句就是重点了.

Isomers are defined as compounds that have the same molecular formula, but different structures.

这个就是定义了. 后面的跟题目并没有直接的关系.
照这个定义去算一下, 图中三个都是一样的.
我的答案并没有错.

举例说明:
题目: 以下三个哪些是人?
      黑人, 白人, 黑白人.

答案: 三个都是人, 可都是不一样的色种. 如此而已.

雨天之魂：

你说的对！是我看错！答案应该是全部都是ISOMERS！谢谢你的提醒！

以下我再给个例子：

“Isomers have the same number of atoms of each element in them and the same atomic weight but differ in other properties. For example, there are two compounds with the molecular formula C 2 H 6 O. One is ethanol (also called ethyl alcohol), CH 3 CH 2 OH, a colorless liquid alcohol; the other is dimethyl ether, CH 3 OCH 3 , a colorless gaseous ether. Among their different properties, ethanol has a boiling point of 78.5°C and a freezing point of -117°C; dimethyl ether has a boiling point of -25°C and a freezing point of -138°C. Ethanol and dimethyl ether are isomers because they differ in the way the atoms are joined together in their molecules”

这次应该是可以完结了吧！哈哈哈！我也差点误人子弟。不好意思！

雨天之魂 于 23-11-2004 23:12  说 :
嗯? 还没完哦?

passerby, ... 你自己不也说了...
第一句就是重点了.



这个就是定义了. 后面的跟题目并没有直接的关系.
照这个定义去算一下, 图中三个都是一样的.
我的答案并没有错.

举例说明:
题 ...

[ Last edited by passerby on 25-11-2004 at 08:06 PM ]