当比较分子结构的极性时，可以考虑以下几个因素：
1. 分子的对称性（Symmetry）：如果分子具有对称轴或中心对称性，通常会减小分子的总极性。对称轴（Symmetry axis）意味着分子可以绕某个轴旋转而不改变其外观，而中心对称（Centrosymmetry）意味着分子的两侧是镜像对称的。具有高度对称性的分子通常不会显示明显的极性。
2. 极性键（Polar bonds）：极性键是由不同电负性的原子之间形成的共价键。当一个原子吸引电子更强烈时，它会在分子中形成部分带电荷，使分子变得极性。
3. 分子的几何形状（Molecular geometry）：分子的几何形状也可以影响其极性。同时，一些分子中，即使存在极性键，由于几何构型的影响，正负电荷可能相互抵消，从而减小总极性。
here's the information in English:
When comparing the polarity of molecular structures, you can consider the following factors:
1. Molecular Symmetry: If a molecule has a symmetry axis or centrosymmetry, it usually reduces the overall polarity of the molecule. A symmetry axis means that the molecule can rotate around an axis without changing its appearance, while centrosymmetry means that the molecule's two sides are mirror images of each other. Molecules with high symmetry typically do not exhibit significant polarity.
2. Polar Bonds: Polar bonds are covalent bonds formed between atoms with different electronegativities. When one atom attracts electrons more strongly, it forms a partial charge within the molecule, making the molecule polar.
3. Molecular Geometry: The geometry of a molecule can also influence its polarity. In some molecules, even if polar bonds are present, the geometric configuration may lead to the partial cancellation of positive and negative charges, reducing the overall polarity.
Considering these factors together allows you to analyze the polarity characteristics of a molecule.