Organic Chemistry Reaction Intermediates

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Questions and Answers

What is the primary result of homolytic bond fission?

Formation of free radicals (correct)

Creation of carbocations

Production of benzyne

Formation of carbanions

Which of the following describes a carbocation?

Divalent with 2 unshared electrons

Positive charge on carbon (correct)

Neutral with an odd electron

Negative charge on carbon

Which reaction intermediate is characterized by having a negative charge on carbon?

Carbocation

Carbene

Carbanion (correct)

Free radical

What hybridization is typically associated with a free radical?

sp2 Signup and view all the answers

Which statement accurately describes the stability of a carbocation?

Carbocations are generally more stable than free radicals. Signup and view all the answers

What type of species is a carbene considered to be?

Divalent with 2 unshared electrons Signup and view all the answers

Which of the following reaction intermediates is paramagnetic?

Free radical Signup and view all the answers

What is the nature of a carbanion?

Negative charge on carbon Signup and view all the answers

What is the result of the reaction involving benzene diazonium halide and alkali?

Formation of diphenyl and nitrogen gas Signup and view all the answers

Which of the following is NOT a type of addition reaction?

Photodynamic additions Signup and view all the answers

Which statement about allylic bromination by NBS is true?

It selectively brominates at the allylic position Signup and view all the answers

What is the main characteristic of the Wurtz reaction?

It involves free radical mechanisms Signup and view all the answers

Electrophilic addition reactions are primarily associated with which type of compounds?

Alkenes Signup and view all the answers

What are nitrenes considered analogous to?

Carbenes Signup and view all the answers

Which of the following can yield unsubstituted nitrene through photolysis?

Ammonia Signup and view all the answers

What type of compound is classified as a neutral nucleophile?

A compound with complete octet and lone pairs Signup and view all the answers

Which reaction involves the decomposition of azides under heat or light?

Formation of nitrenes Signup and view all the answers

Which of the following is an example of an attacking reagent that can form nitrogen nucleophiles?

R3N Signup and view all the answers

What characterizes neutral nucleophiles?

Ability to donate electron pairs Signup and view all the answers

What must be true about the central atom in a neutral nucleophile?

It must have a complete octet Signup and view all the answers

Which of the following statements about azides is accurate?

They can produce nitrenes when decomposed. Signup and view all the answers

What is the electron donating power of the alkyl group in alkyl benzene primarily influenced by?

The number of resonating structures available Signup and view all the answers

Which type of directing group is the alkyl group in electrophilic aromatic substitution?

Ortho-para directing and activating Signup and view all the answers

What effect explains the meta directing influence of the CX3 group?

Hyperconjugation Signup and view all the answers

Which alkyl group displays the highest electron donating power?

C3H7- Signup and view all the answers

What is the effect of having multiple chlorine substituents on the electron donating ability of alkyl groups?

It reduces the electron donating power Signup and view all the answers

Which of the following is a characteristic of an activating group in electrophilic aromatic substitution?

It increases the reaction rate and directs to ortho-para positions Signup and view all the answers

What property of a substituent determines if it will be ortho-para or meta directing in electrophilic aromatic substitution?

The ability to stabilize the carbocation intermediate Signup and view all the answers

Which statement accurately describes the relationship between the number of hydrogens on the alpha carbon and electron donating power?

More hydrogens provide more donating power Signup and view all the answers

What is the molecularity of SN2 reactions?

Bimolecular Signup and view all the answers

Which of the following statements is true for SN1 reactions?

The transition state features a carbocation. Signup and view all the answers

Which compound has the strongest leaving ability based on the given order?

CF3-S-O Signup and view all the answers

What is the rate law for SN2 reactions?

Rate = K2 [Substrate][Nucleophile] Signup and view all the answers

In terms of increasing nucleophilicity, which of the following is ranked correctly?

F- < OH- < NH2- < CH3- Signup and view all the answers

In SN2 reactions, how does the nucleophile attack the substrate?

From the back side exclusively Signup and view all the answers

Which type of organic reaction involves the replacement of an atom or group in a substrate?

Substitution reactions Signup and view all the answers

Which order represents the reactivity of alkyl halides in SN2 reactions?

Methyl > 1° > 2° > 3° Signup and view all the answers

What type of stereochemical outcome occurs in SN1 reactions?

Inversion and retention of configuration Signup and view all the answers

What is the correct decreasing order of leaving ability for the compounds provided?

CF3-S-O > Br > S-O > CH3-S-O Signup and view all the answers

Among the following groups, which is the weakest base?

F- Signup and view all the answers

Which factor is NOT associated with SN1 reactions?

Bimolecular kinetics Signup and view all the answers

What is the overall rate order of SN1 reactions?

First order Signup and view all the answers

Which coupling best represents the increasing order of basicity?

CH3- < NH2- < OH- < F- Signup and view all the answers

Which of the following reactions are categorized as elimination reactions?

Removing a leaving group to develop a double bond Signup and view all the answers

What is the common characteristic of addition reactions?

Involves combining two molecules into a single one Signup and view all the answers

What distinguishes a rearrangement reaction from other types of reactions?

It involves breaking and forming new bonds while preserving the same atoms. Signup and view all the answers

Study Notes

General Organic Chemistry

Carbon is a crucial element in organic compounds, possessing four electrons in its outermost shell. Its ground state electronic configuration is divalent, but tetravalency is explained by promoting a 2s electron to an unoccupied 2p orbital.
These four valencies are similar and arranged symmetrically around the carbon atom in a tetrahedral arrangement, with bond angles of approximately 109.5°.

Hybridization in Organic Compounds

Hybridization involves mixing atomic orbitals to form new, equivalent hybrid orbitals. Three types of hybridization exist:
- sp³: Used in saturated organic compounds (single bonds). Four hybrid orbitals are used.
- sp²: Used in organic compounds with double bonds. Three hybrid orbitals are used, and one p orbital is unused.
- sp: Used in organic compounds with triple bonds. Two hybrid orbitals are used and two p orbitals are unused.
A table showing the relationship between the number of hybrid orbitals used, the number of unused p orbitals, and the percentage of s-character in each type of hybridization.

Determination of Hybridization

Method 1: Determine the hybridisation based on the number of π bonds present on a carbon atom.
Method 2: Electron pair method: ep = bp + lp. ep - electron pairs present in hybrid orbitals, bp - bond pairs present in hybrid orbitals, lp - lone pairs present. The number of bond pairs (bp) is equal to the number of atoms attached to the central atom.
Different orbitals exhibit varying degrees of s-character and electronegativity, influencing the behaviour of carbon in different compounds.

Bond Length and Strength

Different types of carbon-carbon bonds (sp³, sp², sp) have different bond lengths and thus different bond strengths corresponding to the different hybridization of carbon atoms.
Bond length and bond energy are inversely related; shorter bonds have more bond energy, thereby increasing the strength of the bond.

Steric Effect

Steric effects occur in molecules due to the presence of bulky groups that hinder the approach of a reagent. This is known as steric hindrance.
Steric hindrance affects the rate and mechanism of reactions.
Steric strain can restrain resonance.

Inductive Effects

Inductive effects are a way of describing the polarization or polarity that is induced on a chain of carbon atoms by an electron releasing or electron withdrawing X group bonded to a carbon atom on a carbon chain;
Electronegativity of atoms in a covalent bond affects polarity;
Groups with greater electron withdrawing capacity than hydrogen atoms have -I effect (electron withdrawing inductive effect);
Groups with greater electron releasing capacity than hydrogen atoms have +I effect (electron releasing inductive effect);
+I and -I effects follow a decreasing order based on the type of alkyl groups, etc.

Resonance Effect

Resonance or mesomeric effect (M-effect) concerns the electron delocalization in a molecule.
+M and -M effects concern the direction of movement of the π-electrons of a multiple bond either to an atom or to an adjacent single bond or lone pair;

Hyperconjugation

Hyperconjugation involves interaction between π electrons of a multiple bond (e.g., a double bond or a triple bond) and the adjacent σ bonds of alkyl groups, leading to the stabilization of the molecule.
The more the hyperconjugation, the more stable the compound, showing how the alkyl group stabalizes the carbocation, free radical etc.

Addition Reactions

Addition reactions involve the addition of a molecule across a multiple bond (e.g., C=C).

Elimination Reactions

Elimination reactions involve the removal of a molecule from a compound to form a new multiple bond. Often involving a proton (H).

Rearrangement Reactions

Rearrangement reactions involve migrating atoms or groups within a molecule

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Description

Test your knowledge on various organic chemistry reaction intermediates such as carbocations, carbanions, and free radicals. This quiz will challenge your understanding of their characteristics, stability, and hybridization. Perfect for students looking to reinforce their grasp on key concepts in organic chemistry.