Instructions: Cover the answer key, complete each blank, then verify.

1. The C-C bond length in benzene is ______ Å. (1.39)
2. Benzene has ______ pi electrons and satisfies Huckel's rule with n = ______. (6; 1)
3. A compound is aromatic if it has (4n+2) pi electrons AND is ______, ______, and ______. (planar; cyclic; fully conjugated)
4. Cyclobutadiene is ______-aromatic because it has ______ pi electrons (4n, n=1). (anti; 4)
5. COT is ______-aromatic because, although it has 8 pi electrons, it is ______. (non; non-planar/tub-shaped)
6. The electrophile in nitration of benzene is ______. ($NO_{2}^{+}$ / nitronium ion)
7. $NO_{2}^{+}$ is generated by the reaction: $HNO_{3}$ + ______ → $NO_{2}^{+}$ + $HSO_{4}^{-}$ + $H_{2}O$. ($H_{2}SO_{4}$)
8. The Lewis acid catalyst used in halogenation of benzene with $Cl_{2}$ is ______. ($FeCl_{3}$ or $AlCl_{3}$)
9. The EAS intermediate (arenium ion) is also called ______ complex or ______ intermediate. (sigma; Wheland)
10. In EAS, the rate-determining step is step ______ (electrophilic attack / $H^{+}$ loss). (2 / electrophilic attack)
11. The only reversible EAS reaction is ______. (sulfonation)
12. In FC alkylation, the electrophile is ______ (a carbocation). ($R^{+}$)
13. In FC acylation, the electrophile is ______ (an acylium ion). (R$CO^{+}$)
14. FC acylation avoids carbocation rearrangement because the acylium ion is ______-stabilized. (resonance)
15. FC acylation avoids polysubstitution because the -COR product ______ the ring. (deactivates)
16. -OH is an ______ director and ______ (activating/deactivating). (ortho-para; activating)
17. -$NO_{2}$ is a ______ director and ______ (activating/deactivating). (meta; deactivating)
18. Halogens (-Cl, -Br) are ______ directors despite being ______. (ortho-para; deactivating)
19. The ______ effect of halogens makes them overall deactivating but the ______ effect directs to o/p. (-I; +M)
20. -$NH_{2}$ when protonated to -$NH_{3}^{+}$ becomes a ______ director. (meta)
21. The electrophile in FC alkylation using $CH_{3}CH_{2}Cl$ and $AlCl_{3}$ is ______. ($CH_{3}CH_{2}^{+}$ or ethyl carbocation)
22. The SMILES for chlorobenzene is ______. (Clc1ccccc1)
23. The SMILES for nitrobenzene is ______. ([O-][N+](=O)c1ccccc1)
24. The SMILES for toluene is ______. (Cc1ccccc1)
25. Cyclopentadienyl ANION is ______ because it has ______ pi electrons. (aromatic; 6)
26. The standard Huckel number sequence is: 2, ______, 10, 14, 18 ... (6)
27. In benzene, each carbon is ______ hybridized. ($sp^{2}$)
28. Desulfonation occurs by heating $ArSO_{3}H$ with ______ at high temperature. (dilute $H_{2}SO_{4}$)
29. Acylium ion resonance: R-$C^{+}$=O ↔ R-C≡______. ($O^{+}$)
30. The reagent for FC acylation to produce acetophenone from benzene is ______. ($CH_{3}COCl$ / acetyl chloride)
31. Friedel-Crafts reactions fail on strongly ______ rings (e.g., nitrobenzene). (deactivated)
32. -COOH is a ______ director and ______ (activating/deactivating). (meta; deactivating)
33. The product of Friedel-Crafts acylation of benzene with $CH_{3}COCl$ is ______ (SMILES). (CC(=O)c1ccccc1)
34. The two Kekule structures of benzene are ______ contributors. (resonance)
35. In EAS, the aromatic ring acts as a ______ (nucleophile/electrophile). (nucleophile)
36. The three conditions for aromaticity per Huckel: (a) ______, (b) ______, (c) ______. (planar; cyclic; fully conjugated [all ring atoms have p-orbital])
37. Fuming $H_{2}SO_{4}$ is used in sulfonation because ______ is the actual electrophile. ($SO_{3}$)
38. In the resonance structure of aniline (+M effect), the -$NH_{2}$ group places negative charge at ______ positions. (ortho and para)
39. Benzene reacts with $Br_{2}$ without a catalyst to give ______ (addition/substitution). (No reaction without Lewis acid; with $FeBr_{3}$ → substitution to ArBr)
40. The product of mononitration of chlorobenzene is predominantly ______ (positional descriptor). (ortho- and para-chloronitrobenzene)