26. Which of the following statement is false about a-form of Glucose?
(a) It has OH group same side as .
(b) It has m.p. 419 K.
(c) It is formed by crystallization at 371 K.
(d) It is less stable than -form.
Answer:
(a) It has OH group same side as .
Explanation:
In the alpha-anomer of D-glucose (viewed in a standard Haworth projection), the anomeric hydroxyl group at C1 points down, while the group at C5 points up. They are on opposite sides (trans), making statement (a) false.
Direct nitration of aniline with a strongly acidic nitrating mixture protonates the amino group to form an anilinium ion (a meta-directing group). This results in a significant amount of m-nitroaniline (47%), along with p-nitroaniline (51%) and o-nitroaniline (2%).
(b) 2-bromo-4-methylaniline (Structure with NH2, CH3, Br)
Explanation:
Bromination of p-nitrotoluene occurs at the position ortho to the activating methyl group (and meta to the deactivating nitro group). Subsequent reduction with Sn/HCl converts the group to an group, yielding 2-bromo-4-methylaniline.
Vigorous oxidation of tetralin (tetrahydronaphthalene) or o-dialkylbenzenes with hot acidic cleaves the saturated ring, oxidizing the benzylic carbons to yield phthalic acid.
Formaldehyde () lacks alpha-hydrogen atoms. When treated with concentrated alkali, it undergoes a Cannizzaro reaction (a disproportionation) to form an alcohol (methanol) and the salt of a carboxylic acid (potassium formate).
