Formation of Hemiacetals

Q.

What is meant by the following terms ? Give an example of the reaction in each case.

Cyanohydrin

Acetal

Semicarbazone

Aldol

Hemiacetal

Oxime

Ketal

Imine

2, 4 - DNP derivative

Schiff's base

Q. 31. A carbonyl compound reacts with hydrogen cynide to form cyanohydrin which on hydrolysis forms a racemic mixture of alfa-hydroxy acid. The carbonyl compound is 1) acetone 2) diethyl ketone 3) formaldehyde 4) acetaldehyde

Q. Acetyl bromide reacts with excess of $C{H}_{3}MgI$ followed by treatment with a saturated solution of $N{H}_{4}Cl$ gives

1. Acetyl iodide
2. Acetone
3. Acetamide
4. 2 – methyl – 2 – propanol

Q.

Draw structures of the following derivatives.

(i) The 2, 4-dinitrophenylhydrazone of benzaldehyde

(ii) Cyclopropanone oxime

(iii) Acetaldehydedimethylacetal

(iv) The semicarbazone of cyclobutanone

(v) The ethylene ketal of hexan-3-one

(vi) The methyl hemiacetal of formaldehyde

Q. Compounds having general formula
is called:

1. diesters
2. acid anhydrides
3. hemiacetals
4. acetals

Q. In the following reaction:
Aldehyde + Alcohol $\stackrel{HCl}{\to }$ Acetal
Aldehyde Alcohol
$HCHO$ ${}^{t}BuOH$
$C{H}_{3}CHO$ $MeOH$
The best combinations is:

1. $HCHO\text{and}{}^{t}BuOH$
2. $C{H}_{3}CHO\text{and}{}^{t}BuOH$
3. $HCHO\text{and}MeOH$
4. $C{H}_{3}CHO\text{and}MeOH$

Q.

How will you convert ethanal into but-2-enoic acid?

Q. When formaldehyde is treated with methanol in presence of dry HCI gas or fused CaC2, it yields: (a) acetaldehyde (b) mercaptal (c) methylal D (d) dimethyl ether

Q. Acetophenone when reacted with a base, C2HONa, yields a stable compound which has thestructure?\lbrack AIPMT (Prelims)-2008\rbrack

Q. What is meant by the following terms ? Give an example of the reaction in each case.
(i) Cyanohydrin (ii) Acetal (iii) Semicarbazone
(iv) Aldol (v) Hemiacetal (vi) Oxime
(vii) Ketal (vii) Imine (ix) 2, 4-DNP-derivative
(x) Schiffs base

Q. X is .

1. acetal
2. hemiacetal
3. alcohol

Q. Predict the product 'P' of the given reaction.

1. 
2. 
3. 
4. 

Q. An alkyl bromide is formed as the major product on reaction of 3-methyl-2-butene with hydrobromic acid under thermodynamic conditions. Which of the following is the coned name of this-product ?

1. 2-brorno-3-rnethylbutane
2. 1-bromo-3-methylbmane
3. 2-bromo-2-methylbutane
4. 1-bromo-3-methyl-2-butene

Q. 12. Which compound is formed when enolate of 2-methylcyclohexanone , formed from lithium diisopropylamide(LDA), reacts with methyl amide?

Q. Assertion :Aldol condensation can be catalysed both by acids and bases. Reason: $\beta$ Hydroxy aldehydes or ketones readily undergo acid catalysed dehydration.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
3. Assertion is correct but Reason is incorrect.
4. Both Assertion and Reason are incorrect.

Q. Assertion :Aldol condensation can be catalysed both by acids and bases. Reason: $\beta$-Hydroxy aldehydes or ketones readily undergo acid catalysed dehydration.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q. which one is correct regarding hemiacetal formation:

1. $NaOH$ act as nucleophile for carbonyl
2. $NaOH$ increase electrophilicity of acetone.
3. $NaOH$ increase nucleophilicity of methanol.
4. None of the above

Q.
The product "P" in the above reaction is:

1. 
2. 
3. 
4. 

Q. Which of the following is an anti-knocking compound, that has been phased out in many countries so far?

1. Lead tetrachloride
2. Tetra Ethyl Lead
3. Ethyl tetrachloride
4. None of these

Q. What will be the product by reaction ofmethyl amine with nitrous acid? is it ether or alcoho

Q.

how to convert methyl chloride to acetone?

Q. which one is correct regarding hemiacetal formation:

1. $NaOH$ act as nucleophile for carbonyl
2. $NaOH$ increase electrophilicity of acetone.
3. $NaOH$ increase nucleophilicity of methanol.
4. None of the above

Q.

Draw structures of the following derivatives

The 2, 4- dinitro phenyl hydrazone of benzaldehyde

Cyclopropanone oxime

Acetaldehyde dimethyl acetal

The semicarbazone of cyclobutanone

They ethylene ketal of hexan-3-one

The methyl hemiacetal of formaldehyde

Q. X is .

1. acetal
2. hemiacetal
3. alcohol

Q. An organic compound A with molecular formula C₅H₁₁Br when treated with alc.KOH forms B which with H₂O in H₂SO₄(dil) gives C.Compound C when treated with PBr₃ gives D which is an isomer of A.
D with Na in dry ether gives E, structure of which is different when A reacts with Na.
Identify A, B, C, D, E. Write suitable chemical reactions to show the conversion. Write the IUPAC name of each of the compounds.

Q. In aldol condensation, $H^{\oplus }$ is abstracted from the $C$ atom ______ places away from carbonyl $C$.

Q. What happens when?:-
(iii) Acetyl chloride is distilled with sodium acetate.

Q. X is .

1. acetal
2. hemiacetal
3. alcohol

Q. ${CH}_3{CH}_{2}CO{CH}_2{CH}_3$ reacts with hydrogen cyanide to form an organic product called a cyanohydrin.
Which statement is correct?

1. The cyanohydrin product is formed by electrophilic addition
2. The cyanohydrin product has one chiral centre
3. The cyanohydrin product is formed via an intermediate which contains a $C-OH$ group.
4. The formation of the cyanohydrin product requires the use of cyanide ions as a catalyst