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| Names | |
|---|---|
| Preferred IUPAC name 2-(2,5-bis(3,3-dimethylbut-1-yn-1-yl)-4-{[3,5-di(pent-1-yn-1-yl)phenyl]ethynyl}phenyl)-1,3-dioxolane | |
Other names
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| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| UNII | |
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| Properties | |
| C39H42O2 | |
| Molar mass | 542.763 g·mol−1 |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
NanoPutians are a series of organic molecules whosestructural formulae resemble human forms.[1]James Tour's research group designed and synthesized these compounds in 2003 as a part of a sequence onchemical education for young students.[2] The compounds consist of twobenzene rings connected via a few carbon atoms as the body, fouracetylene units each carrying analkyl group at their ends which represents the hands and legs, and a1,3-dioxolane ring as the head. Tour and his team at Rice University used the NanoPutians in their NanoKids educational outreach program. The goal of this program was to educate children in the sciences in an effective and enjoyable manner. They have made several videos featuring the NanoPutians as anthropomorphic animated characters.
Construction of the structures depends onSonogashira coupling and other synthetic techniques. By replacing the 1,3-dioxolane group with an appropriate ring structure, various other types of putians have been synthesized, e.g. NanoAthlete, NanoPilgrim, and NanoGreenBeret. Placingthiol (R-SH) functional groups at the end of the legs enables them to "stand" on agold surface.
"NanoPutian" is aportmanteau ofnanometer, a unit of length commonly used to measure chemical compounds, andlilliputian, a fictional race of humans in the novelGulliver's Travels byJonathan Swift.
While there are no chemical or practical uses for the NanoKid molecule or any of its known derivatives outside of the classroom,James Tour has turned the NanoKid into a lifelike character to educate children in the sciences. The goals of the outreach program, as described on the NanoKids website, are:
To accomplish these goals, several video clips, CDs, as well as interactive computer programs were created. Tour and his team invested over $250,000 into their project. In order to raise the funds for this endeavor, Tour used unrestricted funds from his professorship and small grants from Rice University, theWelch Foundation, the nanotech firmZyvex, andTexas A&M University. Tour also received $100,000 in 2002 from the Small Grants for Exploratory Research program, a division of theNational Science Foundation.[4]
The main characters in the videos are animated versions of the NanoKid. They star in several videos and explain various scientific concepts, such as theperiodic table,DNA, andcovalent bonding.
Rice conducted several studies into the effectiveness of using the NanoKids materials. These studies found mostly positive results for the use of the NanoKids in the classroom. A 2004–2005 study in two schools districts in Ohio and Kentucky found that using NanoKids led to a 10–59% increase in understanding of the material presented. Additionally, it was found that 82% of students found that NanoKids made learning science more interesting.[5]
To create the first NanoPutian, dubbed the NanoKid,1,4-dibromobenzene wasiodinated insulfuric acid. To this product, “arms”, or 3,3-Dimethylbutyne, were then added throughSonogashira coupling. Formylation of this structure was then achieved through using theorganolithium reagentn-butyllithium followed by quenching withN,N-dimethylformamide (DMF) to create the aldehyde. 1,2-Ethanediol was added to this structure to protect the aldehyde usingp-toluenesulfonic acid as acatalyst. Originally, Chanteau and Tour aimed to couple this structure with alkynes, but this resulted in very low yields of the desired products. To remedy this, thebromide was replaced withiodide through lithium-halogen exchange and quenching by using1,2-diiodoethane. This created the final structure of the upper body for the NanoKid.[1]
The synthesis of NanoPutian’s lower body begins withnitroaniline as a starting material. Addition of Br2 inacetic acid places two equivalents ofbromine on thebenzene ring. NH2 is anelectron donating group, and NO2 is anelectron withdrawing group, which both direct bromination to the meta position relative to the NO2 substituent. Addition ofNaNO2,H2SO4, andEtOH removes the NH2 substituent. TheLewis acid SnCl2, areducing agent in THF/EtOH solvent, replaces NO2 with NH2, which is subsequently replaced by iodine upon the addition of NaNO2, H2SO4, and KI to yield 3,5-dibromoiodobenzene. In this step, theSandmeyer reaction converts the primary amino group (NH2) to a diazonium leaving group (N2), which is subsequently replaced by iodine. Iodine serves as an excellent coupling partner for the attachment of the stomach, which is executed through Sonogashira coupling withtrimethylsilylacetylene to yield 3,5-dibromo(trimethylsilylethynyl)benzene. Attachment of the legs replaces the Br substituents with 1-pentyne through another Sonogashira coupling to produce 3,5-(1′-Pentynyl)-1-(trimethylsilylethynyl) benzene. To complete the synthesis of the lower body, the TMS protecting group is removed by selective deprotection through the addition of K2CO3, MeOH, and CH2Cl2 to yield 3,5-(1′-Pentynyl)-1-ethynylbenzene.[1]
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To attach the upper body of the NanoKid to the lower body, the two components were added to a solution ofbis(triphenylphosphine)palladium(II) dichloride,copper(I) iodide,TEA, andTHF. This resulted in the final structure of the NanoKid.[1]
NanoProfessionals have alternate molecular structures for the top of the head, and possibly include a hat. Most can be synthesized from the NanoKid by anacetal exchange reaction with the desired 1,2- or 1,3- diol, usingp-toluenesulfonic acid as catalyst and heated bymicrowave irradiation for a few minutes. The ultimate set of products was a recognizably diverse population of NanoPutians: NanoAthlete, NanoPilgrim, NanoGreenBeret, NanoJester, NanoMonarch, NanoTexan, NanoScholar, NanoBaker, and NanoChef.[2]
The majority of the figures are easily recognizable in their most stableconformation. A few have as their stable conformation a less recognizable shape, so these are often drawn in the more recognizable but less stable way. Many liberties were taken in the visual depiction of the head dressings of the NanoPutians.[2] Some products are formed as a mixture ofdiastereomers—the configuration of the "neck" compared to parts of the "hat".[1]
3-Butyn-1-ol was reacted withmethanesulfonyl chloride andtriethanolamine to produce itsmesylate. The mesylate was displaced to make thiolacetate. The thiol was coupled with 3,5-dibromo(trimethylsilylethynyl)benzene to create a free alkyne. The resulting product, 3,5-(4’-thiolacetyl-1’-butynyl)-1-(trimethylsilylethynyl)-benzene, had its trimethylsilyl group removed usingtetra-n-butylammonium fluoride (TBAF) and AcOH/Ac2O in THF. The free alkyne was then coupled with the upper body product from the earlier synthesis. This resulted in a NanoKid with protected thiol feet.[1]
To make the NanoKid “stand’, the acetyl protecting groups were removed through the use ofammonium hydroxide in THF to create the free thiols. A gold-plated substrate was then dipped into the solution and incubated for four days.Ellipsometry was used to determine the resulting thickness of the compound, and it was determined that the NanoKid was upright on the substrate.[1]
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Synthesis of the upper part of the NanoPutian chain begins with 1,3-dibromo-2,4-diiodobenzene as the starting material. Sonogashira coupling with 4-oxytrimethylsilylbut-1-yne produces 2,5-bis(4-tert-butyldimethylsiloxy-1′-butynyl)-1,4-di-bromobenzene. One of the bromine substituents is converted to an aldehyde through an SN2 reaction with the strong base, n-BuLi, and THF in the aprotic polar solvent, DMF to produce 2,5-bis(4-tert-butyldimethylsiloxy-1′-butynyl)-4-bromobenzaldehyde. Another Sonogashira coupling with 3,5-(1′-Pentynyl)-1-ethynylbenzene attaches the lower body of the NanoPutian. The conversion of the aldehyde group to a diether “head” occurs in two steps. The first step involves addition of ethylene glycol andtrimethylsilyl chloride (TMSCl) in CH2Cl2 solvent. Addition of TBAF in THF solvent removes the silyl protecting group.[1]
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