<p><b>環[18]碳</b>或<b>環十八-1,3,5,7,9,11,13,15,17-九炔</b>是碳的同素異形體之一，化學式為<span>C<span><br>18</span></span>，幾乎不溶於水。它是一種<span data-orig-title="环碳" data-lang-code="en" data-lang-name="英語" data-foreign-title="cyclocarbon"><span>環碳</span></span>和多炔，由十八個碳原子以單叄鍵交替構成環。環[18]碳是預測能夠熱力學穩定最小的環[n]碳，理論應變能為72 kcal/mol。</p>


<h2><span id=".E5.8E.86.E5.8F.B2.E5.92.8C.E5.88.B6.E5.A4.87"></span><span id="历史和制备">歷史和製備</span></h2>
<p>早在1991年，便有人對環[18]碳的結構進行預測，並進行過有關計算，但其合成卻在2019年才被IBM和牛津大學的聯合團隊通過環丁酮結構的數個位點進行電化學脫羰基反應製得：</p>

<p>它也可由C<sub>18</sub>Br<sub>6</sub>的脫溴反應製得。</p>
<h2><span id=".E6.80.A7.E8.B4.A8"></span><span id="性质">性質</span></h2>
<p>IBM研究人員發現，環[18]碳的<span data-orig-title="电子结构" data-lang-code="en" data-lang-name="英語" data-foreign-title="electronic structure"><span>電子結構</span></span>由交替的單叄鍵構成，而非累計雙鍵結構，它在理論上是一種半導體。</p><p>在該化合物中，C—C鍵的鍵長為1.36 Å，C≡C的鍵長為1.20 Å。</p>
<h2><span id=".E5.8F.82.E8.80.83.E6.96.87.E7.8C.AE"></span><span id="参考文献">參考文獻</span></h2>

<h2><span id=".E6.8B.93.E5.B1.95.E9.98.85.E8.AF.BB"></span><span id="拓展阅读">拓展閱讀</span></h2>
<p><small>
</small></p><small><ul><li><cite class="citation journal">Sen, Sabyasachi; Seal, Prasenjit; Chakrabarti, Swapan. Explicit role of dynamical and nondynamical electron correlations on broken symmetry inC<sub>4N+2</sub>clusters. Physical Review B. 2006, <b>73</b> (24). <span title="國際標準連續出版物號">ISSN 1098-0121</span>. <span title="數位物件識別號">doi:10.1103/PhysRevB.73.245401</span>.</cite><span title="ctx_ver=Z39.88-2004&amp;rfr_id=info%3Asid%2Fzh.wikipedia.org%3A%E7%8E%AF%EF%BC%BB18%EF%BC%BD%E7%A2%B3&amp;rft.atitle=Explicit+role+of+dynamical+and+nondynamical+electron+correlations+on+broken+symmetry+inC%3Csub%3E4N%2B2%3C%2Fsub%3Eclusters&amp;rft.au=Chakrabarti%2C+Swapan&amp;rft.au=Seal%2C+Prasenjit&amp;rft.aufirst=Sabyasachi&amp;rft.aulast=Sen&amp;rft.date=2006&amp;rft.genre=article&amp;rft.issn=1098-0121&amp;rft.issue=24&amp;rft.jtitle=Physical+Review+B&amp;rft.volume=73&amp;rft_id=info%3Adoi%2F10.1103%2FPhysRevB.73.245401&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal"><span> </span></span></li>
<li><cite class="citation journal">Feyereisen, Martin; Gutowski, Maciej; Simons, Jack; Almlöf, Jan. Relative stabilities of fullerene, cumulene, and polyacetylene structures for C<sub>n</sub>:n=18–60. The Journal of Chemical Physics. 1992, <b>96</b> (4): 2926–2932. <span title="國際標準連續出版物號">ISSN 0021-9606</span>. <span title="數位物件識別號">doi:10.1063/1.461989</span>.</cite><span title="ctx_ver=Z39.88-2004&amp;rfr_id=info%3Asid%2Fzh.wikipedia.org%3A%E7%8E%AF%EF%BC%BB18%EF%BC%BD%E7%A2%B3&amp;rft.atitle=Relative+stabilities+of+fullerene%2C+cumulene%2C+and+polyacetylene+structures+for+C%3Csub%3En%3C%2Fsub%3E%3An%3D18%E2%80%9360&amp;rft.au=Alml%C3%B6f%2C+Jan&amp;rft.au=Gutowski%2C+Maciej&amp;rft.au=Simons%2C+Jack&amp;rft.aufirst=Martin&amp;rft.aulast=Feyereisen&amp;rft.date=1992&amp;rft.genre=article&amp;rft.issn=0021-9606&amp;rft.issue=4&amp;rft.jtitle=The+Journal+of+Chemical+Physics&amp;rft.pages=2926-2932&amp;rft.volume=96&amp;rft_id=info%3Adoi%2F10.1063%2F1.461989&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal"><span> </span></span></li>
<li><cite class="citation journal">Murphy, Veronica L.; Farfan, Camille; Kahr, Bart. Chiroptical structure-property relations in cyclo[18]carbon and its in silico hydrogenation products. Chirality. 2018, <b>30</b> (4): 325–331. <span title="國際標準連續出版物號">ISSN 0899-0042</span>. <span title="數位物件識別號">doi:10.1002/chir.22817</span>.</cite><span title="ctx_ver=Z39.88-2004&amp;rfr_id=info%3Asid%2Fzh.wikipedia.org%3A%E7%8E%AF%EF%BC%BB18%EF%BC%BD%E7%A2%B3&amp;rft.atitle=Chiroptical+structure-property+relations+in+cyclo%5B18%5Dcarbon+and+its+in+silico+hydrogenation+products&amp;rft.au=Farfan%2C+Camille&amp;rft.au=Kahr%2C+Bart&amp;rft.aufirst=Veronica+L.&amp;rft.aulast=Murphy&amp;rft.date=2018&amp;rft.genre=article&amp;rft.issn=08990042&amp;rft.issue=4&amp;rft.jtitle=Chirality&amp;rft.pages=325-331&amp;rft.volume=30&amp;rft_id=info%3Adoi%2F10.1002%2Fchir.22817&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal"><span> </span></span></li></ul></small><small></small><p><small></small>
</p><p><br></p>
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**環 [18] 碳**或**環十八 - 1,3,5,7,9,11,13,15,17 - 九炔**是碳的同素異形體之一，化學式為 C 
18，幾乎不溶於水。它是一種環碳和多炔，由十八個碳原子以單叄鍵交替構成環。環 [18] 碳是預測能夠熱力學穩定最小的環 [n] 碳，理論應變能為 72 kcal/mol。

## 歷史和製備

早在 1991 年，便有人對環 [18] 碳的結構進行預測，並進行過有關計算，但其合成卻在 2019 年才被 IBM 和牛津大學的聯合團隊通過環丁酮結構的數個位點進行電化學脫羰基反應製得：

它也可由 C18Br6 的脫溴反應製得。

## 性質

IBM 研究人員發現，環 [18] 碳的電子結構由交替的單叄鍵構成，而非累計雙鍵結構，它在理論上是一種半導體。

在該化合物中，C—C 鍵的鍵長為 1.36 Å，C≡C 的鍵長為 1.20 Å。

## 參考文獻

## 拓展閱讀

* Sen, Sabyasachi; Seal, Prasenjit; Chakrabarti, Swapan. Explicit role of dynamical and nondynamical electron correlations on broken symmetry inC4N+2clusters. Physical Review B. 2006, **73** (24). ISSN 1098-0121. doi:10.1103/PhysRevB.73.245401.
* Feyereisen, Martin; Gutowski, Maciej; Simons, Jack; Almlöf, Jan. Relative stabilities of fullerene, cumulene, and polyacetylene structures for Cn:n=18–60. The Journal of Chemical Physics. 1992, **96** (4): 2926–2932. ISSN 0021-9606. doi:10.1063/1.461989.
* Murphy, Veronica L.; Farfan, Camille; Kahr, Bart. Chiroptical structure-property relations in cyclo[18]carbon and its in silico hydrogenation products. Chirality. 2018, **30** (4): 325–331. ISSN 0899-0042. doi:10.1002/chir.22817.
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