Epoxide Reactions

Epoxide Formation

In order to form an epoxide, a electron-rich reagent is required, such as an alkene.  Formation of the epoxide occurs in the presence of a peroxide reactant, such as MCPBA or DET.  The choice of reagent depends on the stereo-specificity desired from the reaction.  MCPBA is used to add the epoxide symmetricaly across the double bond, so that substituents that are cis- or trans- remain in this configuration.  The Sharpless asymmetric addition allows the researcher to choose a stereoisomer of DET, referred to as (+) and (-).  This reagent allows for the attack of the peroxide intermediate on only one face of the alkene, allowing for the production of nearly pure enantiomeric excess product, generally >98%!

Ring-opening Reactions

Many of you have probably hear of epoxy-glue, which is a very strong binding agent.  The process usually involves mixing two reagents and you must quickly apply the mixture to the broken items before the expoxy hardens.  One tube will contain the resin, or epoxide, while the other contains the “hardening” agent, which is the nucleophile that will attack the epoxide.  In a ring-opening reaction, a molecule such as TETA, which contains 4 amino groups, will attack 4 equivalents of oxirane to produce a complex polymer, which is the basis for a strong glue.  Changing the size and complexity of the epoxide can allow for flexibility of strength, thermostability and rigidity!

Carboxylic Acids and their Derivatives

Here is a look at a reaction directly from our proven organic chemistry flash card system:

Esterification of Acid Chloride

Overall Big Picture: In this reaction, an acid halide is reacted with an alcohol to give an ester.

Acid Chloride + Alcohol → Ester

Key Tip: A mild base is required to drive the reaction forward.

Key Comparison: This reaction is only possible due to the high reactivity of acid halides for nucleophiles, even weak ones like alcohols.

Mechanism Hint: Collapse of the addition intermediate is propagated by deprotonating by pyridine, which helps to drive the reaction forward.

Note: When this reaction is carried out using p-toluensufonyl chloride (tosyl group), this reaction is a good protecting group for alcohols.

First window: acetyl chloride

Middle window: alcohol, pyridine

Last window: methyl ester

Chemistry MCQ Test Questions

1.	The enthalpy of vaporization of benzene is +35.3 kJ/mol at its boiling point of 80°C. The entropy change in the transition of vapour to liquid at its boiling point is ______. [in J mol–1 K–1] (A) +100 (B) –100 (C) –342 (D) +342	Answer: (B)
2.	The formation of [PtF6]- is the basis for the formation of Xenon fluorides. This is because (A) O2 and Xe have comparable sizes (B) both O2 and Xe are gases (C) O2 and Xe have comparable ionisation energies (D) O2 and Xe have comparable electronegativities	Answer: (C)
3.	The formula mass of Mohr's salt is 392. The iron present in it is oxidised by KMnO4 in acid medium. The equivalent mass of Mohr's salt is (A) 392 (B) 31.6 (C) 278 (D) 156	Answer: (A)
4.	The geometry of electron pairs around I in IF5 is (A) Octahedral (B) Trigonal bipyramidal (C) Square pyramidal (D) Pentagonal planar	Answer: (A)
5.	The half life time of 2g sample of radioactive nuclide 'X' is 15 min. The half life time of 1g sample of X is (A) 7.5 min (B) 15 min (C) 22.5 min (D) 30 min	Answer: (B)
6.	The highest magnetic moment is shown by the transition metal ion with the configuration (A) 3d2 (B) 3d5 (C) 3d7 (D) 3d9	Answer: (B)
7.	The IUPAC name of is (A) but-1-enoic acid (B) but-3-enoic acid (C) prop-2-enoic acid (D) pent-4-enoic acid	Answer: (B)
8.	The IUPAC name of the complex [Co (NH3)4Cl2] Cl is (A) tetraammine dichloro cobalt (III) chloride (B) dichloro tetraammine cobalt (III) chloride (C) tetraammine dichloro cobalt (IV) chloride (D) tetraammine dichloro cobalt (II) chloride	Answer: (A)
9.	The mass of glucose that should be dissolved in 50 g of water in order to produce the same lowering of vapour pressure as is produced by dissolving 1 g of urea in the same quantity of water is (A) 1 g (B) 3 g (C) 6 g (D) 18 g	Answer: (B)
10.	The maximum number of possible isomers in 1-bromo-2-methyl cyclobutane is (A) 2 (B) 4 (C) 16 (D) 8	Answer: (B)
11.	The pH of 10-8 M HCI solution is (A) 8 (B) more than 8 (C) between 6 and 7 (D) slightly more than 7	Answer: (C)
12.	The radii of Na+ and Cl- ions are 95 pm and 181 pm respectively. The edge length of NaCl unit cell is (A) 276 pm (B) 138 pm (C) 552 pm (D) 415 pm	Answer: (C)
13.	The reaction C2H5ONa + C2H5I ® C2H5OC2H5 + NaI is known as (A) Kolbe's synthesis (B) Wurtz's synthesis (C) Williamson's synthesis (D) Grignard's synthesis	Answer: (C)
14.	The rms velocity of hydrogen is  times the rms velocity of nitrogen. If T is the temperature of the gas, which of the following is true? (A)  =   (B) (C) (D)	Answer: (D)
15.	The solubility of Ca3(PO4)2 in water is y moles / litre. Its solubility product is (A) 6y4 (B) 36y4 (C) 64y5 (D) 108y5	Answer: (D)

AP Chemistry - Sample MCQ Questions

1.	The amount of heat evolved when 500 cm3 of 0.1 M HCl is mixed with 200 cm3 of 0.2 M NaoH is (A) 2.292 kJ (B) 1.292 kJ (C) 22.9 kJ (D) 0.292 kJ	Answer: (A)
2.	The amount of the heat released when 20 ml 0.5 M NaOH is mixed with 100 ml 0.1 M HCI is ´ kJ. The heat of neutralization is (A) –100 x kJ/mol (B) –50 x kJ/mol (C) +100 x kJ/mol (D) +50 x kJ/mol	Answer: (A)
3.	The atomic numbers of Ni and Cu are 28 and 29 respectively. The electron configuration 1s2 2s2 2p6 3s2 3p6 3d10 represents (A) Cu+ (B) Cu2+ (C) Ni2+ (D) Ni	Answer: (A)
4.	The basicity of aniline is less than that of cyclohexylamine. This is due to (A) +R effect of -NH2 group (B) -I effect of -NH2 group (C) -R effect of -NH2 group (D) hyperconjugation effect	Answer: (A)
5.	The brown ring test for nitrates depends on (A) the reduction of nitrate to nitric oxide (B) oxidation of nitric oxide to nitrogen dioxide (C) reduction of ferrous sulphate to iron (D) oxidising action of sulphuric acid	Answer: (A)
6.	The catalyst used in the preparation of an alkyl chloride by the action of dry HCI on an alcohol is (A) anhydrous AlCl3 (B) FeCl3 (C) anhydrous ZnCl2 (D) Cu	Answer: (C)
7.	The compound which gives turbidity immediately with Lucas reagent at room temperature is ______. (A) butan-2-ol (B) butan-1-ol (C) 2-methyl propan-1-ol (D) 2-methyl propan-2-ol	Answer: (D)
8.	The concentration of a reactant X decreases from 0.1 M to 0.025 M in 40 minutes. If the reaction follows I order kinetics, the rate of the reaction when the concentration of X is 0.01 M will be (A) 1.73 ´ 10-4 M min-l (B) 2.47 ´ 10-4 M min-l (C) 3.47 ´ 10-5 M min-l   (D) 1.73 ´ 10-5 M min-l	Answer: (B)
9.	The conversion of m-nitrophenol to resorcinol involves respectively (A) diazotization, reduction and hydrolysis (B) hydrolysis, diazotization and reduction (C) reduction, diazotization and hydrolysis (D) hydrolysis, reduction and diazotization	Answer: (C)
10.	The correct decreasing order of dipole moment in CH3CI, CH3Br and CH3F is (A) CH3F > CH3CI > CH3Br (B) CH3F > CH3Br > CH3CI (C) CH3CI> CH3F > CH3Br (D) CH3CI> CH3Br > CH3F	Answer: (C)
11.	The decomposition of a certain mass of CaCO3 gave 11.2 dm3 of CO2 gas at STP. The mass of KOH required to completely neutralise the gas is (A) 56 g (B) 28 g (C) 42 g (D) 20 g	Answer: (A)
12.	The density of a gas is 1.964 g dm-1 at 273 k and 76 cm Hg. The gas is (A) CH4 (B) C2H6 (C) CO2 (D) Xe	Answer: (C)
13.	The electronic transitions from n = 2 to n = 1 will produce shortest wavelength in (where n = principal quantum state) (A) Li+2 (B) He+ (C) H (D) H+	Answer: (A)
14.	The empirical formula of a nonelectrolyte is CH2O. A solution containing 3g of the compound exerts the same osmotic pressure as that of 0.05 M glucose solution. The molecular formula of the compound is (A) C2H4O2 (B) CH2O (C) C3H6O3 (D) C4H8O4	Answer: (A)
15.	The energy of an electron in first Bohr orbit of H – atom is – 13.6 eV. The possible energy value of electron in the excited state of Li2+ is (A) –122.4 eV (B) 30.6 eV (C) –30.6 eV (D) 13.6 eV	Answer: (C)

Chemistry objective question Test Handouts

1.	Methyl bromide is converted into ethane by heating it in ether medium with (A) Al (B) Zn (C) Na (D) Cu	Answer: (C)
2.	Monobromination of 2-methylbutane gives how many distinct isomers? (A) One (B) Two (C) Three (D) Four	Answer: (D)
3.	More acidic than ethanol is (A) CH3CH2CH2CH2CH2CH2CH2CH3 (B) CH3CO2CH2CH3 (C) CH3COCH2COCH3 (D) CH3COCH3	Answer: (C)
4.	NO2 is not obtained on heating (A) AgNO3 (B) KNO3 (C) Cu(NO3)2 (D) Pb(NO3)2	Answer: (B)
5.	Number of isomeric forms (constitutional and sterioisomers) for [Rh(en)2(NO2)(SCN)]+ are (A) Three (B) Six (C) Nine (D) Twelve	Answer: (D)
6.	Of the following compounds, the oxime of which shows geometrical isomerism, is (A) Acetone (B) Diethylketone (C) Formaldehyde (D) Benzaldehyde	Answer: (D)
7.	One gram of silver gets distributed between 10 cm3 of molten zinc and 100 cm3 of molten lead at 800°C. The percentage of silver still left in the lead layer is approximately (A) 5 (B) 2 (C) 1 (D) 3	Answer: (D)
8.	Osmotic pressure observed when benzoic acid is dissolved in benzene is less than that expected from theoretical considerations. This is because (A) benzoic acid is an organic solute (B) benzoic acid has higher molar mass than benzene (C) benzoic acid gets associated in benzene (D) benzoic acid gets dissociated in benzene	Answer: (C)
9.	Out of the given two compounds, the vapour pressure of B at a particular temperature is (A) higher than that of A (B) lower than that of A (C) higher or lower than A depending on the size of the vessel (D) same as that of A	Answer: (A)
10.	Paracetamol is (A) Methyl salicylate (B) Phenyl salicylate (C) N-acetyl p-amino phenol (D) Acetyl salicylic acid	Answer: (C)
11.	pH value of which one of the following is NOT equal to one? (A) 0.1 M HNO3 (B) 0.1 M CH3 COOH (C) 50 cm3 0.4 M HCl + 50 cm3 0.2 M NaOH (D) 0.05 M H2SO4	Answer: (B)
12.	Platinum, Palladium and Iridium are called noble metals because (A) Alfred Nobel discovered them (B) They are shining lustrous and pleasing to look at (C) They are found in native state (D) They are inert towards many common reagents.	Answer: (D)
13.	Reaction of formaldehyde and ammonia gives (A) Hexamethylene tetramine (B) Bakelite (C) Urea (D) Triethylene Tetramine	Answer: (A)
14.	Solubility product of a salt AB is 1 ´ 10-8 M2 in a solution in which the concentration of A+ ions is 10-3 M. The salt will precipitate when the concentration of B- ions is kept (A) between 10-8 M to 10-7 M (B) between 10-7 M to 10-6 M (C) >10-5 M (D) <1o sup="sup">-

⁸ M

Answer: (C)

15.

The activation energy of a reaction at a given temperature is found to be
2.303 RT J mol^–1. The ratio of rate constant to the Arrhenius factor is

(A) 0.1

(B) 0.01

(C) 0.001

(D) 0.02

Answer: (A)

Chemistry mcq with answers

1.	In the conversion of X is (A) H2/Pt (B) Zn-Hg/HCl (C) Li/NH3 (D) NaBH4	Answer: (D)
2.	In the conversion of Br2 to , the oxidation number of Br changes from (A) zero to +5 (B) +1 to +5 (C) zero to -3 (D) +2 to +5	Answer: (A)
3.	In the following electron – dot structure, calculate the formal charge from left to right nitrogen atom; (A) –1, –1, +1 (B) –1, +1, –1 (C) +1, –1, –1 (D) +1, –1, +1	Answer: (B)
4.	In the following, the element with the highest ionisation energy is (A) [Ne]3s23p1 (B) [Ne]3s23p3 (C) [Ne]3s23p2 (D) [Ne]3s23p4	Answer: (B)
5.	In the reaction R - X the product B is (A) alkyl chloride (B) aldehyde (C) carboxylic acid (D) ketone	Answer: (C)
6.	In the reaction 2H2O2 ® 2H2O + O2 (A) Oxygen is oxidised only (B) Oxygen is reduced only (C) Oxygen is neither oxidised nor reduced (D) Oxygen is both oxidised and reduced	Answer: (D)
7.	In Tollen's test, aldehydes (A) Are oxidised to acids (B) Are reduced to alcohol (C) Neither reduced nor oxidised (D) Precipitate Ag+ as AgCI	Answer: (A)
8.	In which of the following complex ion, the central metal ion is in a state of sp3d2 hybridisation? (A) [CoF6]3- (B) [Co(NH3)6]3+ (C) [Fe(CN)6]3- (D) [Cr (NH3)6]3+	Answer: (A)
9.	In which one of the given formulae of xenon compounds there are five a-bonds and three p-bonds in it? (A) XeFO (B) XeF2O2 (C) XeF3O2 (D) XeF2O3	Answer: (D)
10.	Increasing order of carbon-carbon bond length for the following is C2H4        C2H2        C6H6        C2H6 (A)        (B)        (C)        (D) (A) C < B < A < D (B) B < C < A < D (C) D < C < A < B (D) B < A < C < D	Answer: (D)
11.	Inductive effect involves (A) displacement of s electrons (B) delocalisation of p  electrons (C) delocalisation of s  electrons (D) displacement of p  electrons	Answer: (A)
12.	Insulin regulates the metabolism of (A) minerals (B) amino acids (C) glucose (D) vitamins	Answer: (C)
13.	Liquor ammonia bottles are opened only after cooling. This is because (A) it is a mild explosive (B) it is a corrosive liquid (C) it is a lachrymatory (D) it generates high vapour pressure	Answer: (D)
14.	Lowest pKa is associated with	Answer: (C)
15.	Maximum efficiency of a commercial refrigerator which operates between –10° (inside temperature) and 25°C (outside temperature) is (A) 13.3% (B) 11.45% (C) 24.75% (D) 20%	Answer: (B)