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with David Walton Paul Seheult; Eye Ubiquitous/CORBIS

with David Walton Paul Seheult; Eye Ubiquitous/CORBIS. C 1 ≡ C 2 − C 3 ≡ C 4 − C 5 ≡ C 6 − C 7 ≡ C 8 − C 9 ≡ C 10 − C 11 ≡ C 12 − C 13 ≡ C 14 − C 15 ≡ C 16 − C 17 ≡ C 18 − C 19 ≡ C 20 − C 21 ≡ C 22 − C 23 ≡ C 24 − C 25 ≡ C 26 − C 27 ≡ C 28 − C 29 ≡ C 30 − C 31 ≡ C 32.

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with David Walton Paul Seheult; Eye Ubiquitous/CORBIS

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  1. with David Walton Paul Seheult; Eye Ubiquitous/CORBIS

  2. C1≡C2−C3≡C4−C5≡C6−C7≡C8−C9≡C10−C11≡C12−C13≡C14−C15≡C16−C17≡C18−C19≡C20−C21≡C22−C23≡C24−C25≡C26−C27≡C28−C29≡C30−C31≡C32C1≡C2−C3≡C4−C5≡C6−C7≡C8−C9≡C10−C11≡C12−C13≡C14−C15≡C16−C17≡C18−C19≡C20−C21≡C22−C23≡C24−C25≡C26−C27≡C28−C29≡C30−C31≡C32 David Walton could make very long carbon chains indeed – with 32 carbon atoms!

  3. Cu R−C≡C−H + H−C≡C−R → R−C≡C−C≡C−R + H2O O

  4. O H H O R−C≡C−H H−C≡C−R R−C≡C−C≡C−R Cucatalysed oxidative coupling David Walton

  5. partial cleavage (desilylation) of the products by alkali and reaction KCN R−C≡C−C≡C−R Anthony Alexander - Undergrad Student Sussex 1974

  6. partial cleavage (desilylation) of the products by alkali and reaction KCN R−C≡C−C≡C−R → R−C≡C−C≡C−H Anthony Alexander - Undergrad Student Sussex 1974

  7. partial cleavage (desilylation) of the products by alkali and reaction KCN R−C≡C−C≡C−R → R−C≡C−C≡C−H → R−C≡C−C≡C−CN Anthony Alexander - Undergrad Student Sussex 1974

  8. partial cleavage (desilylation) of the products by alkali and reaction KCN R−C≡C−C≡C−R → R−C≡C−C≡C−H → R−C≡C−C≡C−CN → H−C≡C−C≡C−CN Anthony Alexander - Undergrad Student Sussex 1974

  9. Copper catalysed oxidative coupling Silyl-protected terminal alkynes R = SiEt3 Cu R−C≡C−H + H−C≡C−R → R−C≡C−C≡C−R + H2O O Walton technique

  10. O R−C≡C−H H−C≡C−R Cu R−C≡C−H + H−C≡C−R → R−C≡C−C≡C−R + H2O O

  11. Copper catalysed oxidative coupling Silyl-protected terminal alkynes R = SiEt3 Cu R−C≡C−H + H−C≡C−R → O Walton technique

  12. Cu-catalysed oxidative couplings silyl-protected terminal alkynes, partial cleavage (desilylation) of the products by alkali, recoupling and complete desilylation. Et3SiC≡CH → Et3Si(C≡C)2SiEt3 coupling of the silyidiyne Et3Si(C≡C)2H gives Et3Si(C≡C)4SiEt3 which upon controlled cleavage yields a chromatographically separable mixture of, Et3Si(C≡C)4H and H(C≡C)4H

  13. Individual polyynes in the series H(C C)n (n = 4–10, 12) have been prepared in solution by sequences involving Cu-catalysed oxidative couplings (Hay technique) of silyl-protected terminal alkynes, partial cleavage (desilylation) of the products by alkali, recoupling and complete desilylation. Thus using the conditions established in a model coupling, Et3SiC CH(I) → Et3Si(C SiEt3(II), coupling of the silyidiyne Et3Si(C C)2H(II) gives Et3Si(C C)4SiEt3(IV) which upon controlled cleavage yields a chromatographically separable mixture of IV, Et3Si(C C)4H (V) and H(C C)4H (VI). Coupling of V in turn gives Et3Si(C C)18SiEt3 (VII) which upon cleavage yields Et3Si(C C)8H (VIII) and H(C C)8H (IX), and coupling of VIII gives the bissilylhexadecaacetylene Et3Si(C C)16SiEt3(X). Hexa- and dodecaacetylene may be synthesized analogously: Et3Si(C C)3SiEt3 (XII) → Et3Si(C C)3H (XI) → Et3Si(C )6SiEt3 (XIII) → Et3Si(C C)6H (XIV) → H(C C)6H (XV); XIV → Et3Si(C C)12SiEt3 (XVI) → H(C C)12H (XVII). Other members of the series are prepared via mixed couplings: I + V → Et3Si(C C)5SiEt3 (XVIII) → H(C C)5H (XIX): I + XIV → Et3Si(C C)7SiEt3 (XX) → H(C C)7H (XXI); I + VIII → Et3Si(C C)9SiEt3 (XXII) → H(C C)9H (XXIII): III + VIII → Et3Si(C C)10SiEt3 (XXIV) → H(C C)10H (XXV). The principal UV light absorption maxima of compounds IV → XXV within each of the series Et3Si(C C)nSiEt3, Et3Si(C )nH and H(C C)nH correlate excellently with relationships previously established for polyyne spectra: λ2 = kn (λ = longest wavelength high intensity band) and Δλ = k′n (Δλ = average vibrational spacing of the intense bands).

  14. Individual polyynes in the series H(C C)n (n = 4–10, 12) have been prepared in solution by sequences involving Cu-catalysed oxidative couplings (Hay technique) of silyl-protected terminal alkynes, partial cleavage (desilylation) of the products by alkali, recoupling and complete desilylation. Thus using the conditions established in a model coupling, Et3SiC CH(I) → Et3Si(C SiEt3(II), coupling of the silyidiyne Et3Si(C C)2H(II) gives Et3Si(C C)4SiEt3(IV) which upon controlled cleavage yields a chromatographically separable mixture of IV, Et3Si(C C)4H (V) and H(C C)4H (VI). Coupling of V in turn gives Et3Si(C C)18SiEt3 (VII) which upon cleavage yields Et3Si(C C)8H (VIII) and H(C C)8H (IX), and coupling of VIII gives the bissilylhexadecaacetylene Et3Si(C C)16SiEt3(X). Hexa- and dodecaacetylene may be synthesized analogously: Et3Si(C C)3SiEt3 (XII) → Et3Si(C C)3H (XI) → Et3Si(C )6SiEt3 (XIII) → Et3Si(C C)6H (XIV) → H(C C)6H (XV); XIV → Et3Si(C C)12SiEt3 (XVI) → H(C C)12H (XVII). Other members of the series are prepared via mixed couplings: I + V → Et3Si(C C)5SiEt3 (XVIII) → H(C C)5H (XIX): I + XIV → Et3Si(C C)7SiEt3 (XX) → H(C C)7H (XXI); I + VIII → Et3Si(C C)9SiEt3 (XXII) → H(C C)9H (XXIII): III + VIII → Et3Si(C C)10SiEt3 (XXIV) → H(C C)10H (XXV). The principal UV light absorption maxima of compounds IV → XXV within each of the series Et3Si(C C)nSiEt3, Et3Si(C )nH and H(C C)nH correlate excellently with relationships previously established for polyyne spectra: λ2 = kn (λ = longest wavelength high intensity band) and Δλ = k′n (Δλ = average vibrational spacing of the intense bands).

  15. Cu-catalysed oxidative couplings (Hay technique) silyl-protected terminal alkynes, partial cleavage (desilylation) of the products by alkali, recoupling and complete desilylation. Et3SiC CH(I) → Et3Si(C SiEt3(II), coupling of the silyidiyne Et3Si(C C)2H(II) gives Et3Si(C C)4SiEt3(IV) which upon controlled cleavage yields a chromatographically separable mixture of IV, Et3Si(C C)4H (V) and H(C C)4H (VI). Coupling of V in turn gives Et3Si(C C)18SiEt3 (VII) which upon cleavage yields Et3Si(C C)8H (VIII) and H(C C)8H (IX), and coupling of VIII gives the bissilylhexadecaacetylene Et3Si(C C)16SiEt3(X). Hexa- and dodecaacetylene may be synthesized analogously: Et3Si(C C)3SiEt3 (XII) → Et3Si(C C)3H (XI) → Et3Si(C )6SiEt3 (XIII) → Et3Si(C C)6H (XIV) → H(C C)6H (XV); XIV → Et3Si(C C)12SiEt3 (XVI) → H(C C)12H (XVII). Other members of the series are prepared via mixed couplings: I + V → Et3Si(C C)5SiEt3 (XVIII) → H(C C)5H (XIX): I + XIV → Et3Si(C C)7SiEt3 (XX) → H(C C)7H (XXI); I + VIII → Et3Si(C C)9SiEt3 (XXII) → H(C C)9H (XXIII): III + VIII → Et3Si(C C)10SiEt3 (XXIV) → H(C C)10H (XXV). The principal UV light absorption maxima of compounds IV → XXV within each of the series Et3Si(C C)nSiEt3, Et3Si(C )nH and H(C C)nH correlate excellently with relationships previously established for polyyne spectra: λ2 = kn (λ = longest wavelength high intensity band) and Δλ = k′n (Δλ = average vibrational spacing of the intense bands).

  16. Cadiot-Chodkiewicz couplings of arylacetylenes (I), XC6H4C≡CH (X = H; m-Br, -Me; p-F, -NO2, -OMe) with bromoethynyl(triethyl)silane(II), BrC≡CSiEt3, yield the silylated diynes, XC6H4(C C)2SiEt3, from which the terminal diynes(III), XC6H4C C)2H, are quantitatively liberated by treatment with aqueous methanolic alkali. Reactions of II with III in turn yield the silylated triynes, XC4H4C C)3SiEt3, which, with alkali, give the free arylhexatriynes, XC6H4(C C)3H(IV). The germanium analogue of II, BrC CGeEt3, likewise couples with I (X = H, p-NO2) to give XC6H4(C C)2GeEt3 or with III to give XC6H4(C C)3GeEt3. The products (X = H) are identical with those obtained from the Grignard reagents, C6H5(C=C)nMgBr (n = 2, 3), and bromotriethylgermane. Other XC6H4(C C)nGeEt3 compounds (n = 2,3; excluding X = NO2) were also prepared by the Grignard method. Couplings between phenylacetylene and the reagents, BrC CSiMe3(V), and IC CSiR3 (R = Me, Et) give the appropriate silylated phenylbutadiynes in poor yield because of symmetrical oxidative coupling (iodo compounds) or of base-sensitivity of the trimethylsilyl-acetylene bonds.

  17. Cadiot-Chodkiewicz couplings of arylacetylenes (I), XC6H4C≡CH (X = H; m-Br, -Me; p-F, -NO2, -OMe) with bromoethynyl(triethyl)silane(II), BrC≡CSiEt3, yield the silylated diynes, XC6H4(C≡C)2SiEt3, from which the terminal diynes(III), XC6H4(C≡C)2H, are quantitatively liberated by treatment with aqueous methanolic alkali.

  18. Cadiot-Chodkiewicz couplings of arylacetylenes (I), XC6H4CCH (X = H; m-Br, -Me; p-F, -NO2, -OMe) with bromoethynyl(triethyl)silane(II), BrC CSiEt3, yield the silylated diynes, XC6H4(C C)2SiEt3, from which the terminal diynes(III), XC6H4C C)2H, are quantitatively liberated by treatment with aqueous methanolic alkali. Reactions of II with III in turn yield the silylated triynes, XC4H4C C)3SiEt3, which, with alkali, give the free arylhexatriynes, XC6H4(C C)3H(IV). The germanium analogue of II, BrC CGeEt3, likewise couples with I (X = H, p-NO2) to give XC6H4(C C)2GeEt3 or with III to give XC6H4(C C)3GeEt3. The products (X = H) are identical with those obtained from the Grignard reagents, C6H5(C=C)nMgBr (n = 2, 3), and bromotriethylgermane. Other XC6H4(C C)nGeEt3 compounds (n = 2,3; excluding X = NO2) were also prepared by the Grignard method. Couplings between phenylacetylene and the reagents, BrC CSiMe3(V), and IC CSiR3 (R = Me, Et) give the appropriate silylated phenylbutadiynes in poor yield because of symmetrical oxidative coupling (iodo compounds) or of base-sensitivity of the trimethylsilyl-acetylene bonds.

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