The decrease in electron density increases the polarity of O-H bond and results in the increase in ionization of phenols. a) The–NO2 is electron–withdrawing and acid–strengthening. MCQ Questions for Class 12 Chemistry with Answers were prepared based on the latest exam pattern. Log in. Hence, in alcohols, the oxygen of the –OH group is attached to carbon by a sigma(σ) bond formed by the overlap of an sp3 hybridized orbital of carbon with an sp3 hybridized orbital of oxygen. Phenols react with aqueous sodium hydroxide too to produce phenoxide ions. Your email address will not be published. by Charles Friedel and James Craft in 1877. The greater acidity of phenol owes itself primarily to an electrical charge distribution in phenols that causes the –OH oxygen to be more positive; therefore the proton is held less strongly. Nitro group is an electron-withdrawing group. This alkene on ozonolysis gives single product with molecular formula C2H4O. The reaction takes place with HBr or HI because these reagents are sufficiently acidic. Phenoxide ion has greater stability than phenols, as in the case of phenol charge separation takes place during. A compound X with the molecular formula C2H8O can be oxidised to another compound Y whose molecular formulae is C3H6O2. In terms of resonance and inductive effects we can account for the following relative acidities. In this compound, a hydrogen atom of methane (a hydrocarbon) is replaced by a -OCH3 group. The considerably greater acid strength of PhOH (pKa = 10) than that of ROH (pKa = 18) can be accounted for as the negative charge on the alkoxide anion, RO–, cannot be delocalized, but on PhO–  the negative charge is delocalized to the ortho and para ring positions as indicated by the starred sites in the resonance hybrid. Acidic Nature of Phenol . In the reaction for dinitrated product X is The major dinitrated product X is (a) (b) (c) (d) [2009] Chemistry MCQs for JEE-Main | Phenols MCQ Practice Sheet Answer key: 1. d 2. b 3. Preparation of ethers by reacting sodium ethoxide with alkyl halide is called Williamson synthesis. It weakens the O-H bond of phenol by withdrawing their electrons and thus releases H+ ion easily while due to +I, +R effect of OCH 3, o-methoxy phenol is less acidic. Its resonance effect, which occurs only from para and ortho positions, predominates over its inductive effect, which occurs also from the meta position. If you have any query regarding CBSE Class 12 Chemistry Alcohols, Phenols, and Ethers MCQs Pdf, drop a comment below and we will get back to you at the earliest. a) H 3 N + CH 2 CO 2 H and H 3 N + CH 2 CO 2 - b) H 2 NCH 2 CO 2 H and H 3 N + CH 2 CO 2 - What would be the reactant and reagent used to obtain 2, 4-dimenthyl pentan-3-ol? Answer. शिक्षण प्रक्रिया में शिक्षक को अनेक कार्य एक साथ करने पड़ते हैं जैसे लिखना, प्रश्न पूछना, स्पष्ट करना, प्रदर्शन करना आदि... शिक्षण कौशल ( Teaching Skill) It was first isolated in the early nineteenth century from coal tar. Check the below NCERT MCQ Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers with Answers Pdf free download. Benzoic acid (C 6 H 5 COOH) will not form phenol or phenoxide. Which of the follow ing compounds will be most easily attacked by an electrophile? So, heptyl comes first, followed by phenyl and ending in ‘ether’, as it is a common name. 1. Destructive distillation of wood C. Methane D. All 22. The acidity of phenols is due to its ability to lose hydrogen ion to form phenoxide ions. Methanol is highly poisonous. Methanol can be obtained from A. Check the below NCERT MCQ Questions for Class 12 Chemistry Chapter 11 Alcohols, Phenols and Ethers with Answers Pdf free download. Such reactions generally require a catalyst, such as copper. Sweet potato is not used as a source for making ethanol commercially. They are also known as carbolic acids. ... Read more Alcohols Phenols and Ethers MCQs Therefore, the common name is Ethylphenyl ether. On the other hand, the acidity of phenols decreases in the presence of electron-donating groups as they prohibit the formation of phenoxide ion. It decreases electron density on benzene ring and delocalizes negative charge of phenoxide ion. Free PDF Download of CBSE Chemistry Multiple Choice Questions for Class 12 with Answers Chapter 11 Alcohols, Phenols and Ethers. The cleavage of ethers takes place with concentrated HI or HBr at high temperature. For example, C2H5OC2H5(diethylether). Tertiary alcohols produce turbidity immediately as they form halides easily. Anaerobic means without oxygen.

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