氮孤对电子、电荷及聚合物连接位点
引入
词汇
| English | 释义 | 拼音 |
|---|---|---|
| amine/ˈæmaɪn/ | 胺 | àn |
| zwitterion/zwɪˈtɪərɪən/ | 两性离子 | liǎng xìng lí zi |
| polyamide/ˌpɒlɪˈeɪmaɪd/ | 聚酰胺 | jù xiān àn |
| hydrogen bonds/ˈhaɪdrədʒn bɒndz/ | 氢键 | qīng jiàn |
English
Follow the nitrogen lone pair
- An amine 胺 accepts H⁺ through its nitrogen lone pair. Alkyl groups generally increase electron density and basicity relative to ammonia.
- In phenylamine, interaction with the ring makes the lone pair less available. Its basicity is lower.
English
Keep the nitrile carbon
- Reducing propanenitrile with LiAlH₄ in dry ether then work-up gives propan-1-amine. The nitrile carbon remains in the chain.
- Nitrobenzene instead needs Sn/HCl to make phenylammonium salt; alkali then releases phenylamine.
练习
丙腈还原为胺时，剩余多少个碳原子？
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三个碳原子均保留，包括腈基中的碳。
English
Track both amino-acid groups
- A zwitterion 两性离子 has NH₃⁺ and COO⁻ groups and zero net charge. In strong acid, COO⁻ becomes COOH.
- In strong alkali, NH₃⁺ becomes NH₂ while COO⁻ remains. Glycine is achiral because its central carbon has two H atoms.
Example
Glycine’s alkaline form is H₂NCH₂COO⁻, with net charge −1, not the zero-charge zwitterion.
练习
甘氨酸在强碱环境下的主要存在形式是哪个？
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碱会脱去铵基上的质子，而羧基保持去质子化状态。
练习
甘氨酸是非手性分子，因为中心碳原子连接了两个相同的_____原子。
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两个相同的氢取代基阻止了具有四个不同基团的手性中心的形成。
English
Locate the polymer backbone
- A polyamide 聚酰胺 has –C(=O)–NH– links in its backbone. Condensation produces those links and a small molecule.
- Poly(propenamide) instead opens C=C by addition. Its amide side groups do not make the reaction condensation.
练习
所有带有酰胺侧基的聚合物均由缩聚反应形成。
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聚丙烯酰胺是一种带有酰胺侧基的加聚聚合物。
English
Explain properties through interactions
- Polyamide N–H and C=O groups form hydrogen bonds 氢键 between chains. These help hold fibres together.
- Poly(ethenol) OH groups hydrogen-bond to water, supporting suitable water-soluble laundry-bag applications.
Watch out
The presence of an amide group alone does not classify the polymerisation route.
Key idea
Locate the nitrogen lone pair and its availability before comparing bases. Read the actual reacting groups and links to distinguish addition from condensation polymerisation.
练习
哪两个基团在聚酰胺链之间形成氢键？
难度 2/5 · 今日首次完成可获 140 金币及少量额外奖励
N–H 可作为氢键供体，羰基氧可作为氢键受体。