PRISMANE 棱晶烷

PRISMANE

650-42-0 cas

Tetracyclo[2.2.0.02,6.03,5]hexane

Prismane is a polycyclic hydrocarbon with the formula C₆H₆. It is an isomer of benzene, specifically a valence isomer. Prismane is far less stable than benzene. The carbon (and hydrogen) atoms of the prismane molecule are arranged in the shape of a six-atomtriangular prism. Albert Ladenburg proposed this structure for the compound now known as benzene.^[1] The compound was not synthesized until 1973.^[2]

Prismane
IUPAC name[hide] Tetracyclo[2.2.0.02,6.03,5]hexane
Identifiers
CAS number	650-42-0
ChemSpider	16736515
Jmol-3D images	Image 1
SMILES [show]
InChI [show]
Properties
Molecular formula	C6H6
Molar mass	78.11 g mol−1

History

In the mid 19th century, investigators proposed several possible structures for benzene which were consistent with its empirical formula, C₆H₆, which had been determined by combustion analysis. The first, which was proposed by Kekulé in 1867, later proved to be closest to the true structure of benzene. This structure inspired several others to propose structures that were consistent with benzene's empirical formula; for example, Ladenburg proposed prismane, Dewar proposed Dewar benzene, and Koerner and Claus proposedClaus' benzene. Some of these structures would be synthesized in the following years. Prismane, like the other proposed structures for benzene, is still often cited in the literature, because it is part of the historical struggle toward understanding the mesomeric structures and resonance of benzene. Some computational chemists still research the differences between the possible isomers of C₆H₆.^[3]

Properties

Prismane is a colourless liquid at room temperature. The deviation of the carbon-carbon bond angle from 109° to 60° in a triangle leads to a high ring strain, reminiscent of that of cyclopropane but greater. The compound is explosive, which is unusual for a hydrocarbon. Due to this ring strain, the bonds have a low bond energy and break at a low activation energy, which makes synthesis of the molecule difficult; Woodward and Hoffmann noted that prismane's thermal rearrangement to benzene is symmetry-forbidden, comparing it to "an angry tiger unable to break out of a paper cage."^[4]

The substituted derivative hexamethylprismane (in which all six hydrogens are substituted by methyl groups) has a higher stability, and was synthesized by rearrangement reactionsin 1966.^[5]

Synthesis

The synthesis starts from benzvalene (1) and 4-phenyltriazolidone, which is a strong dienophile. The reaction is a stepwise Diels-Alder like reaction, forming a carbocation as intermediate. The adduct (2) is then hydrolyzed under basic conditions and afterwards transformed into a copper(II) chloride derivative with acidic copper(II) chloride. Neutralized with a strong base, the azo compound (3) could be crystallized with 65% yield. The last step is a photolysis of the azo compound. This photolysis leads to a biradical which forms prismane (4) and nitrogen with a yield of less than 10%. The compound was isolated by preparative gas chromatography.

SYNTHESIS

MeLi, CH2Cl2, 
Et2O
-45 °C, 45 %

+

Et2O, Dioxane
0 °C to RT, 60 min, 50-60 %

KOH, 
MeOH, H2O
Reflux, 24 h

CuCl2, HCl,
H2O
65 % (2 steps)

hν, 
PhMe
30 °C, 5 h, 8 %

References	J. Am. Chem. Soc. 1973, 95, 2738. J. Am. Chem. Soc. 1971, 93, 3782.

https://www.beilstein-journals.org/bjoc/single/printArticle.htm?publicId=1860-5397-7-30

http://chemistry.stackexchange.com/questions/8898/does-benzene-have-isomers-and-resonance-structures

References

1. Ladenburg A. (1869). "Bemerkungen zur aromatischen Theorie". Chemische Berichte 2: 140–2. doi:10.1002/cber.18690020171.
2. Katz T. J., Acton N. (1973). "Synthesis of Prismane". Journal of the American Chemical Society 95 (8): 2738–2739. doi:10.1021/ja00789a084.
3.  UD Priyakumar, TC Dinadayalane, GN Sastry (2002). "A computational study of the valence isomers of benzene and their group V hetero analogs". New J. Chem. 26 (3): 347–353.doi:10.1039/b109067d.
4. R. B. Woodward and R. Hoffmann, Angew. Chem., Int. Ed. Engl., 8, 789, (1969)
5.  Lemal D. M., Lokensgard J. P. (1966). "Hexamethylprismane". Journal of the American Chemical Society 88 (24): pp 5934–5935. doi:10.1021/ja00976a046.

Multi-step synthesis using modular flow reactors: the preparation of yne-ones and their use in heterocycle synthesis

Multi-step synthesis using modular flow reactors: the preparation of yne-ones and their use in heterocycle synthesis 

I.R. Baxendale, S.C. Schou, J. Sedelmeier, S.V. Ley, Chem. Eur. J. 2010, 16, 89-94.

 http://onlinelibrary.wiley.com/doi/10.1002/chem.200902906/abstract

 

Multi-step in flow: The palladium-catalysed acylation of terminal alkynes for the synthesis of yneones as well as their further transformation to various heterocycles in a continuous-flow mode is presented. Furthermore, an extension of the simple flow configuration that allows for easy batch splitting and the generation of a heterocyclic library is described (see scheme).

CH2 Adds Something to Fullerenes

CH₂ Adds Something to Fullerenes

Methylene addends in fullerene electron acceptors increase solar-cell efficiency
Read more



 Fullerene derivatives are used as electron acceptors in organic solar cells. CH₂ addends can effectively raise fullerene lowest unoccupied molecular orbital (LUMO) energy levels, which leads to high open-circuit voltage (V_oc). As the smallest addend, CH₂ does not affect fullerene packing in the solid state, thus keeping good electron mobility for the acceptors.


 http://www.chemistryviews.org/details/ezine/6508231/CH2_Adds_Something_to_Fullerenes.html

Carbohydrate Orientation

 

 

Carbohydrate Orientation

Incorporation of a photosensitive azobenzene linker for controllable carbohydrate orientation
Read more



 Carbohydrate recognition is an important biological process that is essential for the communication between cells, such as cellular adhesion and recognition. A control of the spatial orientation of these carbohydrate units could potentially be used to modify this recognition event.

 http://www.chemistryviews.org/details/ezine/6533751/Carbohydrate_Orientation.html

Remold Crystals with Vapor

Remold Crystals with Vapor

Halogen bonding drives the conversion from surface-confined crystals to co-crystals without the use of solvent
Read more



 The ultimate application of functional materials requires successful fabrication of devices. For organic molecules, this usually involves the deposition of organic thin films on surfaces, which often limits the options for subsequent modification and optimization.


 http://www.chemistryviews.org/details/news/6543561/Remold_Crystals_with_Vapor.html

Mechanism for pyrrole synthesis

This shows the tradtional mechanism for forming a pyrrole ring using a 1,4-diketone and ammonia. The hydroxyl groups are removed as water in two separate dehydration steps, forming enamines in two of the intermediates.
A new mechanism, which does not require enamine formation, has been proposed based on a study using Density Functional Theory.


This shows the mechanism for pyrrole synthesis based on recent DFT study. Instead of the formation and cyclisation of a enamine intermediate, a hemiaminal intermediate in formed, followed by the consecutive dehydrations of the two hydroxyl groups. The dehydration steps may look familiar: it is just the formation of an enamine






A more traditional approach to the mechanism, which appears in some text books and taught courses, can be found here.

 
 
This mechanism was based on the paper: B. Mothana, R. J. Boyd, J. Mol. Struct.: THEOCHEM, 2007, 811, 97-107

Synthesis of 2-dimethylaminomethyl-cyclohexanone hydrochloride

Synthesis of 2-dimethylaminomethyl-cyclohexanone hydrochloride

http://orgspectroscopyint.blogspot.in/2014/09/synthesis-of-2-dimethylaminomethyl.html




++

EtOH, HCl

Synthesis of 2-dimethylaminomethyl-cyclohexanone hydrochloride

Reaction type:	reaction of the carbonyl group in aldehydes, Mannich reaction
Substance classes:	ketone, aldehyde, amine
Techniques:	heating under reflux, stirring with magnetic stir bar, evaporating with rotary evaporator, filtering, recrystallizing, heating with oil bath
Degree of difficulty:	Easy

Equipment

	round bottom flask 25 mL			reflux condenser
	suction filter			suction flask
	heatable magnetic stirrer with magnetic stir bar			rotary evaporator
	exsiccator with drying agent			oil bath

Instruction (batch scale 100 mmol) 

Equipment 

100 mL round bottom flask, reflux condenser, Buechner funnel (Ø 5.5 cm), suction flask, 

heatable magnetic stirrer, magnetic stir bar, rotary evaporator, desiccator, oil bath 

Substances 

cyclohexanone (bp 156 °C) 9.82 g (10.3 mL, 100 mmol) 

paraformaldehyde (mp 120-170 °C) 3.60 g (120 mmol) 

dimethylammonium chloride 8.16 g (100 mmol) 

hydrochloric acid (conc.) 0.4 mL 

ethanol (bp 78 °C) 64 mL 

acetone (bp 56 °C) 180 mL 

Reaction 

9.82 g (10.3 mL, 100 mmol) cyclohexanone, 3.60 g (120 mmol) paraformaldehyde, 8.16 g 

(100 mmol) dimethylammonium chloride and 4 mL ethanol are filled in a 100 mL round 

bottom flask with reflux condenser and magnetic stir bar. 0.4 mL conc. hydrochloric acid are 

added and the mixture is heated under stirring for 4 hours under reflux. 

Work up 

The hot solution is filtered in a round-bottom flask and the solvent is evaporated at the rotary 

evaporator. The residue is dissolved in 20 mL ethanol under heating. At room temperature 

70 mL acetone are added to the solution. For complete crystallization the solution is stored 

over night in the freezer compartment. The crystallized crude product is sucked off over a 

Buechner funnel (Ø = 5.5 cm) and dried in the desiccator over silica gel. 

Crude yield: 15.6 g; mp 149-150 °C 

For further purification the crude product is again dissolved in about 40 mL ethanol under 

reflux and at room temperature 110 mL acetone are added. The crystallization is completed in 

the freezer compartment. The product is sucked off and dried in the desiccator. 

Yield: 14.7 g (76.7 mmol, 77%,); mp 156-157 °C 

Comments 

To verify a complete crystallization, the mother liquor is stored in the freezer compartment. 

No product should crystallize any further.

Simple evaluation indices

Atom economy		not defined
Yield		76	%
Target product mass		1.45	g
Sum of input masses		54	g
Mass efficiency		27	mg/g
Mass index		37	g input / g product
E factor		36	g waste / g product

1H-NMR: 2-Dimethylaminomethyl cyclohexanone hydrochloride
500 MHz, CDCl3
delta [ppm]	mult.	atoms	assignment
1.35	m	1 H
1.54	m	1 H
1.73	m	1 H
1.82	m	1 H
2.05	m	1 H
2.37	m	2 H	6-H (ring)
2.41	m	1 H
2.67	d	3 H	N-CH3
2.74	m	1 H
2.77	d	3 H	N-CH3
3.09	m	1 H	N-CH2
3.57	m	1 H	N-CH2
11.88	m	1 H	N-H
7.26			CHCl3

13C-NMR: 2-Dimethylaminomethyl cyclohexanone hydrochloride
125 MHz, CDCl3
delta [ppm]	assignment
24.70	C5
27.70	C3
33.88	C4
41.75	CH3
42.26	CH3
44.99	C6
46.69	C2
56.80	-CH2-N-
209.58	C1 (C=O)
76.5-77.5	CDCl3

IR: 2-Dimethylaminomethyl cyclohexanone hydrochloride
[Film, T%, cm-1]
[cm-1]	assignment
3068, 3020	N-H valence
2932, 2858	C-H valence
1698	C=O valence, ketone

http://kriemhild.uft.uni-bremen.de/nop/en/instructions/pdf/4008_en.pdf