A new electronic structure of allene
Lakhbir Singh1957, Die Naturwissenschaften
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From Allenes to Tetracenes: A Synthetic and Structural Study of Silyl- and Halo-Allenes and Their Dimers
European Journal of Organic Chemistry, 2007
Keywords: Allenes / Dimerizations / Long bonds 9-Alkynylfluoren-9-ols of type C 13 H 8 (OH)-CϵC-R, where R is phenyl (1a), p-tolyl (1b), p-methoxyphenyl (1c), or trimethylsilyl (1d), react with HBr to yield the corresponding bromoallenes C 12 H 8 C=C=C(Br)R (13a-d). Lithiation and hydrolysis of 13d yields 3,3-(biphenyl-2,2Ј-diyl)-1-(trimethylsilyl)allene (20), which forms successively the head-to-tail dimer 1- and the tail-totail dimer trans-3,4-bis(trimethylsilyl)-1,2-di(fluorenylidene)cyclobutane (23) both of which exhibit long (ca. 1.6 Å) C(3)-C(4) bonds. Treatment of 21 and 23 with TBAF brings about desilylation to 22 and 24, respectively. In the latter case, removal of the bulky trimethylsilyl groups reduces the C(3)-[a] School 2612 (for 13a) appear in parts a,b of Figure 3, respectively. The allene double bonds are, of course, orthogonal and in both cases the C(9)=C(10) bond [1.313(4) Å in 12; 1.321(3) Å in 13a] is significantly longer than the C(10)=C(11)-X bond [1.298(4) Å in 12; 1.292(3) Å in 13a].
Cyclic allenes. I. Electronic structure and probable deformation of the allene linkage when included in a ring. INDO-MO [intermediate neglect of differential overlap-molecular orbitial] study
Journal of the American Chemical Society, 1974
As a model for the medium and small cyclic allenes, INDO-MO calculations have been performed on a large number of distorted geometries of allene. Both the lowest singlet and triplet states were calculated, and the effect of geometrical distortion on total energy, charge distribution, and spin distribution were investigated. The calculations indicate that singlet 1,2-cyclooctadiene and 1,2-cycloheptadiene are probably bent at C-2 and also twisted somewhat from the orthogonal geometries. These distortions also bring about a moderate increase in charge separation, as compared with linear allenes. They further indicate that the singlet states of the smaller cyclic allenes are probably planar and bent. In these cases there is considerable charge delocalization and the allene moiety may best be considered as an allyl cation with an anion located at C-2 in the in-plane sp" orbital. For the triplet state the allene moiety is probably planar in all cases and is bent if the ring contains six or fewer atoms. These systems have little charge separation and may best be visualized as an allyl radical with a second unpaired electron in the in-plane p (or sp") orbital at C-2. Finally the calculations indicate that while 1,2-cycloheptadiene and larger cyclic allenes would have singlet ground states, 1,2-cyclohexadiene and smaller cyclic allenes may have triplet ground states. he synthesis and isolation or trapping of highly
Understanding the 1,3-Dipolar Cycloadditions of Allenes
Chemistry - A European Journal, 2020
We have quantum chemically studied the reactivity,s ite-, and regioselectivity of the 1,3-dipolar cycloaddition between methyl azide and variousa llenes, including the archetypal allenep ropadiene,h eteroallenes, and cyclic allenes, by using density functional theory (DFT). The 1,3-dipolar cycloaddition reactivity of linear(hetero)allenesd ecreases as the number of heteroatoms in the allene increases, and formation of the 1,5-adduct is,i na ll cases, favored overt he 1,4-adduct. Both effects find their origin in the strength of the primary orbital interactions. The cycloaddition reactivity of cyclic allenes was also investigated, and the increased predistortion of allenes, that resultsu pon cyclization, leads to systematicallyl ower activation barriers not due to the expectedv ariations in the strain energy, but instead from the differences in the interaction energy.T he geometricp redistortiono fc yclic allenes enhances the reactivity compared to lineara llenest hrough au nique mechanism that involves a smaller HOMO-LUMO gap, which manifestsa sm ore stabilizing orbitalinteractions.
Theoretical Study of Heavier Group 14 Analogues of Allene
Organometallics, 2002
We report the first systematic computational study, using both ab initio and DFT methods, of the heavier group 14 analogues of allene: R 2 MdCdCH 2 and H 2 CdMdCH 2 , M) Si, Ge, Sn and Pb, where the substituents R are H, Me, SiH 3 , and F. The following trends were observed (mostly at B3LYP/SDD): (a) 1-metalaallenes are more stable than 2-metalaallenes for all M elements; (b) in both 1-and 2-metalaallenes the deviation of the skeleton from linearity, the degree of pyramidalization at M, and the planarization energies at M decrease along the series Pb > Sn > Ge > Si; the silaallenes, except for F 2 SidCdCH 2 , are linear and planar at silicon; (c) the SiH 3 substituent favors planarization at M, while F substitution causes strong pyramidalization.
ChemInform Abstract: Ambiphilic Allenes: Synthesis and Reactivity
ChemInform, 2009
Ambiphilic allenes are generated by an organocatalyzed domino reaction of alkyl propiolates and aromatic 1,2-diketones; in the absence of any external chemical agent, these allenes perform a thermally-driven dimerization reaction to generate the corresponding fully-substituted cyclobutanes in a regio-and highly stereoselective manner.
Ambiphilic allenes: synthesis and reactivity
Chemical Communications, 2009
Ambiphilic allenes are generated by an organocatalyzed domino reaction of alkyl propiolates and aromatic 1,2-diketones; in the absence of any external chemical agent, these allenes perform a thermally-driven dimerization reaction to generate the corresponding fully-substituted cyclobutanes in a regio-and highly stereoselective manner.
Isomerization of Allene and Polyene
We report the isomerization energies of cumulene and poly-yne oligomeric sequences calculated using several different theoretical methods in an attempt to evaluate both the performance of these methods and their potential application to similar systems. We find that the recently developed KMLYP density functional theory method reproduces the CCSD(T) benchmark relative energies better than other commonly used quantum chemical methods. Furthermore, the KMLYP relative energies scale significantly better with molecule length with an average error of 0.6 kcal/mol per additional C 2 monomer. The B3LYP, B3PW91, mPW1PW91, and BXLYP methods scale with errors of 2.3, 2.4, 2.0, and 2.1 kcal/mol per additional C 2 monomer, respectively, while the MP2, MP4(SDQ), and CCSD methods scale with errors of 2.6, 1.4, and 1.4 kcal/mol, respectively. Consequently, these methods have large errors for chain lengths above C 5 . The Hartree-Fock (HF) method is surprisingly successful in calculating the enthalpy difference between shortest cumulene/poly-yne isomers, allene and propyne. This appears to be the result of a fortuitous equivalence of correlation energies for these two molecules as HF adds an additional error of 5.1 kcal/mol per additional C 2 unit. We point out how this equivalence makes the allene/propyne system useful as a testing ground for the ability of quantum chemical methods to capture correlation energy.
The silyl-cupration and stannyl-cupration of allenes
Tetrahedron, 1989
Printed in Great Britain. 004+4020/89 %3.OO+.Kl 0 1989 Pergamon Press plc 7 I, 8-13 7 18-21
The intramolecular amination of allenes
Chemical Communications, 2010
Single crystal X-ray diffraction data were obtained using a Nonius Kappa-CCD area detector diffractometer, with graphite-monochromated Mo-K! radiation (! = 0.71073 Å) at 150 K. Cell parameters and intensity data were processed using the DENZO-SMN package 1 and reflection intensities were corrected for absorption effects by the multi-scan method, based on multiple scans of identical and Laue equivalent reflections. The structures were solved by direct methods using SIR92 2 and refined by full-matrix least squares on F 2 using the CRYSTALS suite 3 as per the details in the CIF.
195 Pt NMR Determination of the Enantiomeric Purity and Absolute Configuration of Trisubstituted Allenes by Using [PtCl 3 (C 2 H 4 )] - [( S , S )-(1-NpMeCH) 2 NH 2 ] + as CDA
Organic Letters, 2001
The ionic CDA [PtCl 3 (C 2 H 4 )] -[(S,S)-(1-NpMeCH) 2 NH 2 ] + produces, on exchange of its coordinated ethylene by chiral trisubstituted allenes, diastereoisomeric mixtures originating distinct 195 Pt NMR resonances for the complexed enantiomers, thus allowing the determination of the enantiomeric purity. A reproducible correlation between relative positions of platinum signals due to the complexed enantiomers and their absolute configuration has been found.
;~36
Kurze Originalmitteilungen
5 ~ gegen < I ~ bet flfissigen Gemischen) n a c h w e i s b a r ist.
Dieses E r g e b n i s e r k l g r t sich a u s der T a t s a c h e , d a b bet Verw e n d u n g y o n s i c h t b a r e m L i c h t die kritische Opaleszenz erst
m e r k l i c h wird, w e n n die K o r r e l a t i o n sich fiber m e h r als 100
erstreckt, w a s n u r wenige Z e h n t e l - G r a d e o b e r h a l b Tk zutrifft.
Der K o n z e n t r a t i o n s b e r e i c h , in d e m der E f f e k t n o c h n a c h w e i s b a r ist, s c h e i n t bet fliissigen u n d f e s t e n L 6 s u n g e n v o n d e r
gleiehen G r 6 S e n o r d n u n g (etwa ZI x m 0,1) zu seth.
Die ausftihrliche M i t t e i l u n g e r s c h e i n t d e m n / i c h s t a n a n d e r e r
Stelle.
~]/Ietall-Laboratorium der Metallgesellscha/t AG., Frank/~trt
a. Main
A. N I ~ N s ~ ] ~ R u n d K. S A G E L
Eingegangen am 23. August 1957
~) MO~STE~, A., u. K. SAU~L: Z. physik. Chem., N.F. a) 12,
145 (~957).b) 7, 296 (195@
A New Electronic Structure of Allene
M o d e r n s t r u c t u r a l theories a p p e a r to be i n a d e q u a t e to
e x p l a i n t h e p h y s i c a l a n d c h e m i c a l p r o p e r t i e s of allene
( C H ~ = C : C H e ) a n d its h i g h e r h o m o l o g u e s . However, t h e n e w
(physical) electronic c o n c e p t of t h e m u l t i p l e - b o n d s d e v e l o p e d
b y t h e a u t h o r ~) a p p e a r s t o elucidate t h e s e s t r u c t u r e s a t l e a s t
in a q u a l i t a t i v e way.
O n t h i s concept, if all t h e four C - - H s i n g l e - b o n d s in allene
are c o p l a n a r as in e t h y l e n e (Fig. t), t h e n t h e d i s t o r t e d g-elect r o n d e n s i t y of C - a t o m "'a" (represented b y t h e d o t t e d line)
Fig. ~. Electronic structure of allene (CH~=C--CH~)
w o u l d interfere w i t h t h e Jr-electron orbit "'3" ( b e l o n g i n g t o t h e
o t h e r double-bond), a n d t h e ~-electron d e n s i t y of t h e C - a t o m "c"
w o u l d o b s t r u c t t h e xc-electron orbit " 2 " . T h e s e ~r--zc electronic s t e r i c - h i n d r a n c e s w o u l d cause t h e r o t a t i o n of one
~ - b o n d w i t h r e s p e c t to t h e o t h e r till t h e y are at r i g h t angles
to each other. I n t h i s p o s i t i o n s u c h h i n d r a n c e s w o u l d be
a l m o s t absent. T h i s a c c o u n t s for t h e n o n c o p l a n a r i t y of t h e
four single-bonds2), w h i c h gives rise to optical i s o m e r i s m in
allene d e r i v a t i v e s 3). However, in b u t a t r i e n e ( > C~C~C-a-C < )
t h e four single-bonds b e c o m e c o p l a n a r again, as t h e ~ - b o n d s
" t " a n d "3" are b o t h at r i g h t angles to t h e s a m e middle
~ - b o n d "2". T h u s , d e r i v a t i v e s of b u t a t r i e n e s h o w c i s - t r a n s
isomerismS).
T h e C = C d o u b l e - b o n d l e n g t h ( 1 ' 3 0 ~ ) in allene 2) is
s i g n i f i c a n t l y s h o r t e r t h a n in e t h y l e n e (t"34 ~), b e c a u s e t h e
~-electron shell of t h e central c a r b o n a t o m in alIene, consisting
of only 2g-electrons, is v e r y s m a l l as in acetylene. O n t h i s
basis it c a n be p r e d i c t e d t h a t t h e m i d d l e d o u b l e - b o n d "2"
in b u t a t r i e n e , for w h i c h b o t h t h e c a r b o n a t o m s are small,
w o u l d be still s h o r t e r (about t.27/~). T h e small r e s u l t a n t
orbital m a g n e t i c m o m e n t s of t h e t w o r
in allene m a y
cancel e a c h o t h e r as in a c e t y l e n e (see Fig. t). T h u s P a s c a l ' s
correction factor t for allene m a y be p r a c t i c a l l y zero a n d for
b u t a t r i e n e it m a y h a v e a p p r o x i m a t e l y t h e v a l u e for one
d o u b l e - b o n d only.
Tile e u m u l e n e s r e s e m b l e p o l y - a c e t y l e n e s in m a n y of t h e i r
p h y s i c a l a n d c h e m i c a l p r o p e r t i e s s u c h as U.V. a b s o r p t i o n
spectraS), c h e m i c a l reactivity6), etc. O n this n e w concept, it
m a y be d u e to t h e c o m m o n s t r u c t u r a l f e a t u r e in t h e m t h a t t h e
i n n e r C - a t o m s in b o t h are s m a l l a n d c o n t a i n only 2 g-electrons
a n d 2~r-electrons each. I t is r e m a r k a b l e t h a t h i g h e r c u m u l e n e s
are q u i t e s t a b l e c o m p o u n d s . T h e i n n e r C - a t o m s ill t h e m , w h i c h
are deficient in g-electrons, m a y h a v e a n electrophilic r e t a r d i n g
effect on t h e r e a c t i v i t y of t h e e n d CH 2 groups.
Note appended: t3. P. STOIClCEFF h a s since c o n f i r m e d exp e r i m e n t a l l y t h a t t h e m i d d l e d o u b l e - b o n d - l e n g t h in b u t a t r i e n e
is t.284 -~ [Can. J. P h y s . 35, 837 (1957)].
National Chemical Laboratory, Poona, India
LAKHBIR SINGH
Eingegangen am 10. Juli 1957
~) SISGH, L.: Naturwiss. 43, 466 (a956); 44, 253 (1957). - ~) OVER~NI), J., and H.W. THO~PSOZ<: J. Opt. Soc. Amer. 43, 1065
(1953). - - ~) MAITLAND, P., and W. FI. MILLS: Nature [London] 135,
Die Natur-
wissensehaften
994 (1935). - - J. Chem. Soc. ~London] 1936, 987. - - 4) K u a x , R.,
and K.L. SCHOLLER: Chem. Ber. 87, 598 (1954). - - ~) BOH~IANN, F.,
and K. KIESLICH: Chem. Ber. 8% 1363 (1954); as, t211 (1955). - 6) BOND, G.C., and J. SHERmAn': Trans. Faraday See. 48, 658
(I952).
Zinkchlorid als Glasbildner
Von den H a l o g e n i d e n ist b i s h e r B e P 2 sis g u t e r Glasbildner
b e k a n n t , d a s SiO2-~hnliehe E i g e n s c h a f t e n aufweist. V o n
t h e o r e t i s c h e m I n t e r e s s e dfirfte es sein, d u g s u c h S c h m e l z e n
a u s Chloriden u n d g e m i s c h t e n H a I o g e n i d e n r e c h t g u t e glasbildende E i g e n s c h a f t e n besitzen k 6 n n e n . So w u r d e n a u s Zinkchlorid u n d g e e i g n e t e n Z u s ~ t z e n eine R e i h e y o n Gi~sern erhaIten.
R e i n e s Zinkchlorid o h n e Z u s a t z bildet eine viskose
Schmelze, die j e d o c h n u t b e i m A b s c h r e c k e n in d i i n n e r S c h i c h t
glasartig e r s t a r r e n k a n n . Die g l a s b i l d e n d e n E i g e n s c h a f t e n
einer ZnCI2-Schme]ze w e r d e n s e h r verbessert, w e n n m a n
K a l i u m h a l o g e n i d e hinzuffigt. So e r s t a r r e n die v i s k o s e n
S c h m e l z e n a u s 1 3/iol ZnC12 u n d t N2ol KC1 oder K B r s c h o n
bet s c h w a c h e m A b s c h r e c k e n als G15~ser. Die b e s t e G l a s b i l d u n g
erfolgt bet Z u s a t z y o n K J . E i n e Schmelze a u s t Mol ZnClz
u n d t Mol K ] h a t s e h r g u t e glasbildende E i g e n s c h a f t e n .
S c h m e l z e n raft a n d e r e m K J - G e h a l t (t0 his 70 G e w . - % K J ,
R e s t ZnC12) sind d u r c h m e h r oder w e n i g e r s t a r k e s A b s c h r e c k e n
ebenfalls leicht glasartig zu erhalten.
Alle diese ZnC12-Naliumhalogenid-GlXser h a b e n einen s e h r
niedrigen T r a n s f o r m a t i o n s p u n k t . So liegt dieser fiir ein ZnC12Glas m i t 50 MoI.-% K J z.B. u n t e r h a l b t00 ~ C. Die Gl~ser
w u r d e n in M e n g e n y o n 5 his 10 g bet 3 5 0 ~ i m P l a t i n t i e g e l
e r s c h m o l z e n ; sie sind alle h y g r o s k o p i s c h .
ZnC12 ergibt n i c h t m u r m i t H a l o g e n i d e n , s o n d e r n s u c h
m i t S u l f a t e n Gt~ser. S c h m e t z e n a u s t Mol ZnC12 n n d {- bis
I Mol Na2SO ~ h a b e n s e h r g u t e glasbildende E i g e n s c h a f t e n .
A u c h m i t KeSO4-Zusatz s i n d Gl~ser zu erhalten. E r w ~ h n t
soil n o c h werden, d a b ZnCI~. a n c h m i t N a t r i u m p y r o - u n d
N a t r i u m m e t a p h o s p h a t Ol~tser bildet.
Berlin N 4, Institut /i& angewandte Silikat/orschung der
lgeutschen Akademie der Wissenscha/ten zu Berlin (Letter: Prof.
Dr. It. H. FRANCK)
INGEBORG SCHULZ
Eingegangen
am
26. August ~957
p-Cresotic Acid - - a Microreagent for Uranium
P r e l i m i n a r y e x p e r i m e n t s in t h e s e L a b o r a t o r i e s s h o w e d
t h a t a n alcoholic solution of p-cresotic (2-hydroxy-3-mefihyl
benzoic) acid p r o d u c e s a n i n t e n s e red colour w i t h a n a q u e o u s
u r a n y l salt solution. I t w a s of i n t e r e s t t h e r e f o r e to s t u d y t h e
s u i t a b i l i t y of t h i s colour reaction for t h e detection of s m a l l
q u a n t i t i e s of u r a n i u m . A s t o c k solution of p u r e u r a n y l
s u l p h a t e or a c e t a t e w a s p r e p a r e d in w a t e r a n d its u r a n i u m
c o n t e n t d e t e r m i n e d b y t h e classical o x i n a t e method~). A b o u t
2 g m of p-cresotic acid (m.pt. t53 ~ C), purified earlier b y
recrystallizing it f r o m h o t water, was dissolved in t 0 0 ml of
80% ethanol. A n a d s o r b e n t p a p e r was s o a k e d in t h e r e a g e n t
solution a n d dried. A drop of t h e t e s t solution was n o w placed
on t h e p a p e r w h e n t h e a p p e a r a n c e of a red s p o t i n d i c a t e d t h e
presence of u r a n i u m . T h e r e s p e c t i v e identification a n d conc e n t r a t i o n limits of t h e p r e s e n t t e s t were f o u n d to be t4 y a n d
one p a r t of t h e e l e m e n t p e r 2,000 p a r t s of t h e soiution. E x c e p t
free acids, Fe(III), Ce(IV), Th, p h o s p h a t e , oxalate, t u n g s t a t e
a n d large c o n c e n t r a t i o n s of Cu, Co, Ni, a n d s u l p h a t e , o t h e r
ions do n o t affect t h e s e n s i t i v i t y of t h e a b o v e test.
A few e x p e r i m e n t s carried o u t w i t h t h e aid of a p h o t o eIectric colorimeter revealed t h a t t h e i n t e n s i t y of t h e red
colour is directly p r o p o r t i o n a l to t h e c o n c e n t r a t i o n of u r a n i u m
s u g g e s t i n g t h e possibiIity of colorimetric d e t e r m i n a t i o n of
u r a n i m n b y p-cresotic acid. T h e s e r e s u l t s will be c o m m u n i c a t e d a t a l a t e r stage.
W e wish to e x p r e s s o u r g r a t e f u l t h a n k s to Prof. S. S. JosHI
for r e s e a r c h facilities a n d advice in t h e work.
Chemical Laboratories, Banaras Hindu University, Banaras
(India)
B . R . SAlT a n d M . K . JosHI*)
Eingegangen am 9. September t957
*) Present Address: Department of Chemistry, N. A. S. College,
Meerut (India).
1) VOGEL, A.I.: A Text Book of Quantitative Inorganic Analysis, p. 557. London: Longmans, Green & Co. t948.
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