Hybridization group

A narrow, sp3 hybridized grouping was required at the keto position. 

In so called homo Diels-Alder reactions, in which double bonds are replaced by three-membered rings or two 7r-bonds of the reactive 1,3-diene are bridged by an sp -hybridized group, a powerful pressure-induced acceleration and hence highly negative activation volumes comparable to those of the ordinary Diels-Alder reactions have been observed. Examples of the pressure effect on homo-Diels-Alder reactions are shown in Scheme 2.7. The reaction of homofuran with fumaronitrile (Scheme 2.7, entry (8)) [52] seems to be an exception in which the activation volume is significantly less negative than those in other cases. With the use of fumaronitrile and maleonitrile ((E)- and (Z)-NC-CH= CH-CN) as dienophiles it was es-... 

Figure 36.1 S Fuel-cell hybrid group 2.0. Reproduced from [7].

As noted above, DBA/2 KLH-primed T cells failed to effectively cooperate with if-2-incompatible DNP-primed C3H B cells (Group V). Similarly, DBA/2 H-2 ) T cells failed to effectively interact with (C3H x C3H.A)Fi B cells, although these B cells carry the /-C, S and D regions derived from the H-2 haplotype (Group VII). In contrast, the same pool of helper T cells from DBA/2 donors were perfectly good helpers in development of secondary anti-DNP responses with hapten-primed B cells from (C3H x C3H.OH)Fi and (C3H X C3H.OL)Fi hybrids (Groups IX and XI). 

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