**Part 1**

**Small Molecules** 

**1** 

*Israel* 

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**Polycyclic Aromatic Ketones –** 

**Study of Acetyl Anthracenes** 

*Edmond J. Safra Campus, Jerusalem* 

**A Crystallographic and Theoretical** 

PPA,140°

Sergey Pogodin, Shmuel Cohen, Tahani Mala'bi and Israel Agranat *Organic Chemistry, Institute of Chemistry, The Hebrew University of Jerusalem,* 

"Acylation differs from alkylation in being virtually irreversible" [Olah, 1973], free of rearrangements and isomerizations [Wang, 2009; Norman & Taylor, 1965]. This authoritative exposition of the state of the art of Friedel–Crafts chemistry in 1973 close to the centennial of the invention of the Friedel–Crafts reaction has been long recognized and not without reason. The difference in behavior between Friedel–Crafts acylation and Friedel– Crafts alkylation was attributed to the resonance stabilization existing between the acyl group and the aromatic nucleus [Buehler & Pearson, 1970], which may serve as a barrier against rearrangements and reversible processes. However, if the acyl group is tilted out of the plane of the aromatic nucleus, e.g., by bulky substituents, the resonance stabilization is reduced and the pattern of irreversibility of Friedel–Crafts acylation may be challenged [Buehler & Pearson, 1970; Pearson & Buehler, 1971; Gore, 1974]. Under these conditions deacylations and acyl rearrangements become feasible [Buehler & Pearson, 1970; Pearson &

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1*Z*-BzNA 2*E*-BzNA

Fig. 1. The Friedel–Crafts acyl rearrangement of 1- and 2-benzoylnaphthalenes in PPA

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The concept of reversibility in Friedel–Crafts acylations [Gore, 1955, 1964] was put forward in 1955 by Gore, who proposed that "the Friedel–Crafts acylation reaction of reactive hydrocarbons is a reversible process" [Gore, 1955]. Gore concluded that "Reversibility is an important factor in acylation reactions" [Gore, 1955]. The reversibility studies have been

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PPA,140°

**1. Introduction** 

Buehler, 1971; Gore, 1974].

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