In host-guest chemistry, to improve the stability of the complex formed between the host molecule and the guest molecule, the structure of the host molecule needs to be pre-organized and designed before the host molecule binds to the guest molecule. This process is called the pre-organization of the host molecule ($pre-organization$). For example, crown ethers (such as $18-$crown$-6$) can be regarded as structures obtained by pre-organizing coordinating oxygen atoms. Such a pre-organized structure enables $18-$crown$-6$ to form a very stable complex with potassium ions.

$25^\degree C, 100 \ kPa$ 下, $K^+$在水溶液中的溶剂化焓 $\Delta_{sov} H_{m}{ }^{\circ}$
$=-76 \ kJ/{mol}$，but the solvation free energy is only $\Delta_{sov} G_{m}{ }^{\circ}=-48 \ kJ/mol$ .

Scientists have synthesized a molecule called spherand, and its structure is shown in the figure below.

<MultiModal>![The following is the structure of the molecule CC1=CC2=C(C(=C1)CC3=CC(=CC(=C3OC)CC4=CC(=CC(=C4OC)CC5=CC(=CC(=C5OC)CC6=C(C(=CC(=C6)C)CC7=C(C(=CC(=C7)C)CC8=C(C(=CC(=C8)C)C2)OC)OC)OC)OC)C)C)C)OC, in which solid wedges and dashed wedges are marked on the $6$ methoxy groups, which means that they have alternating up/down orientations relative to the average plane of the macrocycle (which can be understood as the least squares plane of the center points of the $6$ aromatic rings).
Therefore, the whole molecule approximately has a S₆ (or C₃) symmetrical "alternating conformation": three sites "up" (solid wedge) + three sites "down" (dashed wedge), arranged alternately along the ring.](/media/uploads/a347b0be-fa26-4f6b-9a3c-e226dfbae038.png)</MultiModal>

For the following statements, all the correct options are:

**a**: $25^{\circ} C, 100 \ kPa$ 下，$\Delta_{sov} S_{m}{ }^{\circ}=-94 \ J \cdot mol^{-1} \cdot {K}^{-1}$, the reason for the entropy decrease is that the movement of water molecules bound to potassium ions is restricted, mainly due to the reduction of vibrational degrees of freedom.

**b**: $25^{\circ} C, 100 \ kPa$ 下，$\Delta_{sov} S_{m}{ }^{\circ}=94 \ J \cdot mol^{-1} \cdot {K}^{-1}$, the reason for the entropy increase is that the movement of water molecules bound to potassium ions is restricted, mainly due to the reduction of translational and rotational degrees of freedom.

**c**: In aqueous solution, the pre-organized $18-$crown$-6$ is more likely to bind to $K^+$ than water molecules, and this phenomenon is mainly due to the effect of entropy.

**d**: In aqueous solution, the pre-organized $18-$crown$-6$ is more difficult to bind to $K^+$ than water molecules, and this phenomenon is mainly due to the effect of enthalpy.

**e**: In aqueous solution, the pre-organized $18-$crown$-6$ is more likely to bind to $K^+$ than water molecules, and this phenomenon is mainly due to the effect of enthalpy.

**f**: In aqueous solution, the pre-organized $18-$crown$-6$ is more difficult to bind to $K^+$ than water molecules, and this phenomenon is mainly due to the effect of entropy.

**g**: Compared to $18-$crown$-6$, spherand is more likely to bind to $Li^+$, because the absolute value of the entropy decrease of spherand binding to $Li^+$ is smaller than that of $18-$crown$-6$.

**h**: Compared to $18-$crown$-6$, spherand is more likely to bind to $Li^+$, because the absolute value of the enthalpy change of spherand binding to $Li^+$ is greater than that of $18-$crown$-6$.

**i**: Compared to $18-$crown$-6$, spherand is more difficult to bind to $Li^+$, because the absolute value of the entropy decrease of spherand binding to $Li^+$ is greater than that of $18-$crown$-6$.

**j**: Compared to $18-$crown$-6$, spherand is more difficult to bind to $Li^+$, because the absolute value of the enthalpy change of spherand binding to $Li^+$ is smaller than that of $18-$crown$-6$.

**k**: Compared to $18-$crown$-6$, spherand is more likely to bind to $Li^+$, because the absolute value of the entropy increase of spherand binding to $Li^+$ is greater than that of $18-$crown$-6$.

**l**: Compared to $18-$crown$-6$, spherand is more difficult to bind to $Li^+$, because the absolute value of the entropy increase of spherand binding to $Li^+$ is smaller than that of $18-$crown$-6$.
在主-客体化学中，为提高主体分子与客体分子之间形成的复合物的稳定性，在主体分子与客体分子结合之前，需对主体分子的结构进行预先的组织和设计，这一过程被称为主体分子的预组织($pre-organization$)。例如，冠醚(如$18-$冠$-6$)即可看做是将配位氧原子预组织所得到的结构,这样的预组织结构使得$18-$冠$-6$ 能与钾离子形成非常稳定的络合物。

$25^\degree C, 100 \ kPa$ 下, $K^+$在水溶液中的溶剂化焓 $\Delta_{sov} H_{m}{ }^{\circ}$
$=-76 \ kJ/{mol}$，但溶剂化自由能只有 $\Delta_{sov} G_{m}{ }^{\circ}=-48 \ kJ/mol$ 。

科学家们合成了一种叫球醚($spherand$)的分子, 其结构如下图所示。


<MultiModal>![下文是该分子的结构CC1=CC2=C(C(=C1)CC3=CC(=CC(=C3OC)CC4=CC(=CC(=C4OC)CC5=CC(=CC(=C5OC)CC6=C(C(=CC(=C6)C)CC7=C(C(=CC(=C7)C)CC8=C(C(=CC(=C8)C)C2)OC)OC)OC)C)C)C)OC，图中在$6$ 个甲氧基上标出了实楔与虚楔，意味着它们相对于大环平均面（可以理解成 $6$ 个芳环中心点的最小二乘平面）呈现交替的上/下取向。
因而全分子近似具备 S₆（或 C₃）对称的“交替构象”：三个位点“上”（实楔）+ 三个位点“下”（虚楔），沿环交替排布。](/media/uploads/a347b0be-fa26-4f6b-9a3c-e226dfbae038.png)</MultiModal>

对于下列说法，所有的正确选项是：


**a**：$25^{\circ} C, 100 \ kPa$ 下，$\Delta_{sov} S_{m}{ }^{\circ}=-94 \ J \cdot mol^{-1} \cdot {K}^{-1}$，熵减的原因是与钾离子结合的水分子的运动受到限制，其中主要是振动自由度降低。

**b**：$25^{\circ} C, 100 \ kPa$ 下，$\Delta_{sov} S_{m}{ }^{\circ}=94 \ J \cdot mol^{-1} \cdot {K}^{-1}$，熵增的原因是与钾离子结合的水分子的运动受到限制，其中主要是平动和转动自由度降低。

**c**：水溶液中经过预组织的$ 18-$冠$-6$ 相对于水分子更易与 $K^+$结合，这一现象主要是熵的作用。

**d**：水溶液中经过预组织的$ 18-$冠$-6$ 相对于水分子更难与 $K^+$结合，这一现象主要是焓的作用。

**e**：水溶液中经过预组织的$ 18-$冠$-6$ 相对于水分子更易与 $K^+$结合，这一现象主要是焓的作用。

**f**：水溶液中经过预组织的$ 18-$冠$-6$ 相对于水分子更难与 $K^+$结合，这一现象主要是熵的作用。

**g**：相较于$ 18-$冠$-6$，球醚更易与$Li^+$结合，因为球醚结合$Li^+$的熵减的绝对值比$ 18-$冠$-6$更小。

**h**：相较于$ 18-$冠$-6$，球醚更易与$Li^+$结合，因为球醚结合$Li^+$的焓变的绝对值比$ 18-$冠$-6$更大。

**i**：相较于$ 18-$冠$-6$，球醚更难与$Li^+$结合，因为球醚结合$Li^+$的熵减的绝对值比$ 18-$冠$-6$更大。

**j**：相较于$ 18-$冠$-6$，球醚更难与$Li^+$结合，因为球醚结合$Li^+$的焓变的绝对值比$ 18-$冠$-6$更小。

**k**：相较于$ 18-$冠$-6$，球醚更易与$Li^+$结合，因为球醚结合$Li^+$的熵增的绝对值比$ 18-$冠$-6$更大。

**l**：相较于$ 18-$冠$-6$，球醚更难与$Li^+$结合，因为球醚结合$Li^+$的熵增的绝对值比$ 18-$冠$-6$更小。
**c**，**g**，**h**
**a**，**c**，**g**，**h**
**c**，**g**
**a**，**b**，**c**
**c**，**e**，**i**，**j**
**d**，**f**，**j**，**k**
**a**，**e**，**j**，**i**
**a**，**f**，**g**，**h**
**a**，**g**，**h**
**c**，**g**，**h**
**a**，**c**，**g**，**h**
**c**，**g**
**a**，**b**，**c**
**c**，**e**，**i**，**j**
**d**，**f**，**j**，**k**
**a**，**e**，**j**，**i**
**a**，**f**，**g**，**h**
**a**，**g**，**h**
Obtained from $\Delta_{sov} G_{m}{ }^{\circ}=\Delta_{sov} H_{m}{ }^{\circ}-T \Delta_{sov} S_{m}{ }^{\circ}$: $\Delta_{sov} S_{m}{ }^{\circ}=-94 \ J \cdot mol^{-1} \cdot {K}^{-1}$. The movement of water molecules bound to potassium ions is restricted, resulting in a negative entropy change for the reaction. The reduction in translational and rotational degrees of freedom of multiple water molecules in the potassium ion hydration shell will lead to a significant entropy decrease.

<Checkpoint>[The reduction in translational and rotational degrees of freedom of multiple water molecules in the potassium ion hydration shell will lead to a significant entropy decrease.](1)</Checkpoint>

**a,b** incorrect

Because the structure of $18-$crown$-6$ can be regarded as a structure in which the complexation sites are combined in advance, that is, an entropy reduction process is performed in advance, which leads to a smaller entropy reduction in the $18-$crown$-6$ complexation $K^+$ step than the entropy reduction of hydration. Therefore, $18-$crown$-6$ is more likely to bind to $K^+$ than water molecules. More broadly, ring-forming reactions can be seen as pre-assembling two reaction sites in one molecule, which can effectively reduce the entropy decrease of the reaction.

<Checkpoint>[an entropy reduction process is performed in advance, which leads to a smaller entropy reduction in the $18-$crown$-6$ complexation $K^+$ step than the entropy reduction of hydration](1)</Checkpoint>

Pre-organized $ 18-$crown$-6$ is more likely to bind to $K^+$ than water molecules

<Checkpoint>[Pre-organized $ 18-$crown$-6$ is more likely to bind to $K^+$ than water molecules](1)</Checkpoint>

**c** correct

The process of crown ether complexation with potassium ions and the process of potassium ion hydration are both processes in which oxygen atoms and metal ions generate electrostatic interactions, and the coordination numbers of the metal ions are also similar, so the enthalpy changes of these two processes are not much different, so it is not the effect of enthalpy.

<Checkpoint>[The process of crown ether complexation with potassium ions and the process of potassium ion hydration are both processes in which oxygen atoms and metal ions generate electrostatic interactions, and the coordination numbers of the metal ions are similar, the enthalpy changes of these two processes are not much different](1)</Checkpoint>

**d,e,f** incorrect

Crown ethers are flexible macrocyclic compounds whose carbon-carbon and carbon-oxygen bonds can rotate freely; however, after complexation with $Li^+$, their ring structure becomes rigid, which also leads to entropy reduction. In spherand molecules, due to the steric hindrance of the benzene ring, their structure is very rigid; therefore, the entropy reduction of spherands before and after binding to metal ions is smaller. Spherands pre-expend more entropy than crown ethers before complexation.

<Checkpoint>[the entropy reduction of spherands before and after binding to metal ions is smaller. Spherands pre-expend more entropy than crown ethers before complexation.](1)</Checkpoint>

On the other hand, due to the restriction of the rigid ring system of spherands, the distance between the six oxygen atoms in the spherands is short, and the repulsive force is large; after the spherand complexes with ${Li}^{+}$, the repulsive force between the oxygen atoms is alleviated; therefore, relative to crown ethers, spherand complexation with ${Li}^{+}$ is a reaction with a more negative enthalpy change. Spherands pre-expend more enthalpy than crown ethers before complexation.

<Checkpoint>[the distance between the six oxygen atoms in the spherands is short, and the repulsive force is large; after the spherand complexes with ${Li}^{+}$, the repulsive force between the oxygen atoms is alleviated; relative to crown ethers, spherand complexation with ${Li}^{+}$ is a reaction with a more negative enthalpy change](1)</Checkpoint>

Spherands are more likely to complex with $ Li^+$

**g,h** correct, **i,j,k,l** incorrect

Answer **A** is correct
由 $\Delta_{sov} G_{m}{ }^{\circ}=\Delta_{sov} H_{m}{ }^{\circ}-T \Delta_{sov} S_{m}{ }^{\circ}$ 求得: $\Delta_{sov} S_{m}{ }^{\circ}=-94 \ J \cdot mol^{-1} \cdot {K}^{-1}$。与钾离子结合的水分子的运动受到限制，导致了反应的熵变为负。钾离子水合层的多个水分子平动和转动自由度降低, 会导致严重的熵减。

<Checkpoint>[钾离子水合层的多个水分子平动和转动自由度降低, 会导致严重的熵减。](1)</Checkpoint>

**a,b**错误

因为$18-$冠$-6$的结构可看做是预先将络合位点结合起来的结构，即预先进行了一个熵减的过程，这导致$18-$冠$-6$络合$K^+$步骤中的熵减比水合的熵减更小，因此$18-$冠$-6$比水分子更易与$K^+$结合。更广泛地,成环反应中可以看作将两个反应位点预先组合在一个分子里，可以有效地减少反应的熵减。

<Checkpoint>[预先进行了一个熵减的过程，这导致$18-$冠$-6$络合$K^+$步骤中的熵减比水合的熵减更小](1)</Checkpoint>

经过预组织的$ 18-$冠$-6$ 相对于水分子更易与 $K^+$结合

<Checkpoint>[经过预组织的$ 18-$冠$-6$ 相对于水分子更易与 $K^+$结合](1)</Checkpoint>

**c**正确

冠醚与钾离子络合的过程和钾离子水合的过程均是氧原子和金属离子产生静电作用的过程，且金属离子的配位数也相近，所以这两个过程的焓变相差不大,因此不是焓的作用。

<Checkpoint>[冠醚与钾离子络合的过程和钾离子水合的过程均是氧原子和金属离子产生静电作用的过程，且金属离子的配位数相近，这两个过程的焓变相差不大](1)</Checkpoint>

**d,e,f**错误

冠醚是柔性的大环化合物，其碳碳键和碳氧键可以自由旋转；但与$Li^+$络合后，其环结构变得刚性，也导致了熵减。球醚分子中,由于苯环的位阻作用,导致其结构非常刚性；因此，球醚结合金属离子前后，其熵减更小。球醚比冠醚在络合之前预支了更多的熵。

<Checkpoint>[球醚结合金属离子前后，其熵减更小。球醚比冠醚在络合之前预支了更多的熵。](1)</Checkpoint>

另一方面，由于球醚刚性环系的限制，球醚中六个氧原子间距离较近，排斥力较大；球醚络合了${Li}^{+}$之后，缓解了氧原子间的排斥力；因此,相对于冠醚而言，球醚络合 ${Li}^{+}$是个焓变更负的反应。球醚比冠醚在络合之前预支了更多的焓。

<Checkpoint>[球醚中六个氧原子间距离较近，排斥力较大；球醚络合了${Li}^{+}$之后，缓解了氧原子间的排斥力；相对于冠醚而言，球醚络合 ${Li}^{+}$是个焓变更负的反应](1)</Checkpoint>

球醚更易与$ Li^+$络合 

**g,h**正确，**i,j,k,l**错误

答案**A**正确