Organic chemistry basics
62 flashcards covering Organic chemistry basics for the MCAT Chem / Phys / Psych / Soc section.
Organic chemistry is the study of carbon-containing compounds, which form the foundation of living organisms and everyday materials. At its basics, it explores how carbon atoms bond with hydrogen, oxygen, and other elements to create molecules like alcohols, acids, and hydrocarbons. These concepts help explain chemical reactions in biological processes, such as metabolism, making it essential for understanding life sciences.
On the MCAT, organic chemistry appears in the Chemical and Physical Foundations section, often through multiple-choice questions testing reaction mechanisms, functional groups, and stereochemistry. Common traps include mistaking similar structures or overlooking reaction conditions, so focus on applying concepts to real-world scenarios rather than rote memorization. Expect questions that integrate organic chemistry with biology, like enzyme reactions.
Practice sketching molecules to solidify your understanding.
Terms (62)
- 01
Alkane
Alkanes are hydrocarbons with only single bonds between carbon atoms, making them saturated and generally unreactive except under combustion or halogenation conditions.
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Alkene
Alkenes are hydrocarbons containing at least one carbon-carbon double bond, which allows for addition reactions like hydrogenation or halogenation.
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Alkyne
Alkynes are hydrocarbons with at least one carbon-carbon triple bond, enabling reactions such as addition of halogens or hydration to form alcohols.
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Aromatic compound
Aromatic compounds are cyclic molecules with a planar ring of sp2 hybridized carbons and delocalized electrons, following Hückel's rule, which makes them stable and resistant to addition reactions.
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Functional group
A functional group is a specific group of atoms within a molecule that determines its chemical reactions, such as hydroxyl in alcohols or carbonyl in aldehydes.
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IUPAC nomenclature
IUPAC nomenclature is the systematic method for naming organic compounds based on the longest carbon chain and substituents, ensuring unique identification for molecules like 2-methylpentane.
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Structural isomer
Structural isomers are compounds with the same molecular formula but different connectivity of atoms, such as butane and isobutane, leading to different physical properties.
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Stereoisomer
Stereoisomers are molecules with the same molecular formula and connectivity but different spatial arrangements, including enantiomers and diastereomers, which can affect biological activity.
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Enantiomer
Enantiomers are a pair of stereoisomers that are non-superimposable mirror images, rotating plane-polarized light in opposite directions and often having different interactions with chiral environments.
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Diastereomer
Diastereomers are stereoisomers that are not mirror images, differing at some but not all chiral centers, which results in different physical and chemical properties.
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Chirality
Chirality refers to the property of a molecule that is not identical to its mirror image, typically due to a chiral center like a carbon with four different substituents.
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Optical activity
Optical activity is the ability of a chiral compound to rotate the plane of polarized light, measured by specific rotation, and is a key characteristic of enantiomers.
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SN1 reaction
An SN1 reaction is a two-step nucleophilic substitution where a carbocation intermediate forms first, followed by nucleophile attack, typically favoring tertiary substrates and leading to racemization.
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SN2 reaction
An SN2 reaction is a one-step nucleophilic substitution involving backside attack by the nucleophile, inverting the configuration and favoring primary substrates with strong nucleophiles.
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E1 reaction
An E1 reaction is a two-step elimination reaction forming an alkene via a carbocation intermediate, common with tertiary alcohols under acidic conditions and leading to Zaitsev products.
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E2 reaction
An E2 reaction is a concerted elimination where a base removes a proton and a leaving group departs simultaneously, favoring anti-periplanar geometry and strong bases.
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Electrophile
An electrophile is an electron-deficient species that accepts a pair of electrons from a nucleophile, such as a carbocation or proton, driving many organic reactions.
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Nucleophile
A nucleophile is an electron-rich species that donates a pair of electrons to an electrophile, often negatively charged like hydroxide ion, in substitution or addition reactions.
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Carbocation
A carbocation is a positively charged carbon intermediate with only six valence electrons, making it highly reactive and a key player in SN1 and E1 mechanisms.
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Free radical
A free radical is a species with an unpaired electron, such as the methyl radical, which participates in chain reactions like halogenation of alkanes.
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Substitution reaction
A substitution reaction replaces one atom or group on a molecule with another, such as in SN1 or SN2, and is common in alkyl halides.
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Elimination reaction
An elimination reaction removes atoms or groups from adjacent carbons to form a double bond, as in E1 or E2, often converting alcohols to alkenes.
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Addition reaction
An addition reaction adds atoms or groups across a double or triple bond, such as electrophilic addition to alkenes, increasing molecular saturation.
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Oxidation in organic chemistry
Oxidation in organic chemistry involves loss of electrons or addition of oxygen/bonds to oxygen, like converting a primary alcohol to an aldehyde using PCC.
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Reduction in organic chemistry
Reduction in organic chemistry involves gain of electrons or addition of hydrogen/removal of oxygen, such as reducing an alkene to an alkane with hydrogen and a catalyst.
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Acidity
Acidity measures how readily a compound donates a proton, influenced by factors like resonance and inductive effects, with pKa values indicating strength, such as acetic acid at 4.76.
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pKa value
pKa is the negative logarithm of the acid dissociation constant, indicating acid strength; lower pKa means stronger acid, like HCl with pKa -7 versus ethanol at 15.9.
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Resonance
Resonance describes the delocalization of electrons in molecules with multiple Lewis structures, stabilizing species like benzene and affecting reactivity.
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Inductive effect
The inductive effect is the electron-withdrawing or donating influence through sigma bonds, such as the electron-withdrawing chlorine in chloroacetic acid increasing acidity.
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Hydrogen bonding
Hydrogen bonding is an intermolecular force where a hydrogen atom bonded to electronegative atoms like oxygen interacts with another electronegative atom, affecting boiling points of alcohols.
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Alcohol
Alcohols are organic compounds with a hydroxyl group attached to a carbon, exhibiting properties like hydrogen bonding and undergoing reactions like dehydration to form alkenes.
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Ether
Ethers are compounds with an oxygen atom connected to two alkyl or aryl groups, like diethyl ether, which are relatively unreactive but useful as solvents.
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Aldehyde
Aldehydes are compounds with a carbonyl group at the end of a carbon chain, such as formaldehyde, and they can be oxidized to carboxylic acids or reduced to primary alcohols.
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Ketone
Ketones are compounds with a carbonyl group between two carbon atoms, like acetone, and they undergo nucleophilic addition but are resistant to oxidation.
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Carboxylic acid
Carboxylic acids contain a carboxyl group, making them acidic and capable of forming salts, esters, or undergoing decarboxylation reactions.
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Ester
Esters are derivatives of carboxylic acids with a -COOR group, formed by esterification, and they have pleasant odors and can be hydrolyzed back to acids and alcohols.
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Amine
Amines are organic derivatives of ammonia with nitrogen bonded to carbon groups, acting as bases and participating in reactions like acylation.
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Amide
Amides contain a carbonyl group attached to a nitrogen, like in proteins, and they are less basic than amines due to resonance, resisting hydrolysis.
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Alkyl halide
Alkyl halides have a halogen atom bonded to an alkyl chain, serving as substrates for substitution and elimination reactions.
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Grignard reagent
Grignard reagents are organometallic compounds like CH3MgBr, acting as strong nucleophiles to form alcohols from carbonyl compounds.
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Reaction mechanism
A reaction mechanism is the step-by-step process of how reactants transform into products, involving intermediates and transition states, as in SN2.
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Markovnikov's rule
Markovnikov's rule states that in addition reactions to unsymmetric alkenes, the hydrogen adds to the carbon with more hydrogens, and the electrophile to the other, like in HCl addition to propene.
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Zaitsev's rule
Zaitsev's rule predicts that in elimination reactions, the major product is the more substituted alkene, such as 2-butene from 2-bromobutane.
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Hammond postulate
The Hammond postulate suggests that the transition state resembles the nearest stable species, helping predict reaction rates for exothermic or endothermic steps.
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Kinetics of reactions
Kinetics in organic reactions refers to the rate of reaction, influenced by factors like concentration and temperature, as opposed to the thermodynamic stability of products.
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Arrow pushing
Arrow pushing is a method to illustrate electron movement in reaction mechanisms, using curved arrows to show bond breaking and forming, essential for understanding processes like nucleophilic attack.
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Conjugate acid-base pair
A conjugate acid-base pair consists of two species differing by a proton, like acetic acid and acetate, where the acid donates and the base accepts a proton.
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Leaving group
A leaving group is the part of a substrate that departs with a pair of electrons in substitution or elimination, with good leaving groups like iodide being weak bases.
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Nucleophile strength
Nucleophile strength depends on factors like basicity and polarizability, with strong nucleophiles like OH- favoring SN2 reactions over weak ones like H2O.
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Solvent effects
Solvent effects influence reaction rates and mechanisms, with polar protic solvents favoring SN1 by stabilizing carbocations and polar aprotic favoring SN2 by solvating cations.
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Stereochemistry in reactions
Stereochemistry in reactions determines the spatial outcome, such as inversion in SN2 or racemization in SN1, based on the mechanism and substrate.
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Racemization
Racemization is the process where a chiral compound converts to a 50:50 mixture of enantiomers, often via a planar carbocation intermediate in SN1 reactions.
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Inversion of configuration
Inversion of configuration occurs when the stereochemistry at a chiral center flips, as in SN2 reactions due to backside attack by the nucleophile.
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Protecting group
A protecting group temporarily masks a reactive functional group, like using a silyl group on an alcohol, to prevent unwanted reactions during synthesis.
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IR spectroscopy
IR spectroscopy identifies functional groups by measuring the absorption of infrared light, with peaks corresponding to bond vibrations, such as C=O at around 1700 cm⁻¹.
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NMR spectroscopy
NMR spectroscopy determines molecular structure by analyzing the magnetic environment of nuclei like hydrogen, providing information on chemical shifts and coupling patterns.
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Mass spectrometry
Mass spectrometry measures the mass-to-charge ratio of ions to determine molecular weight and fragmentation patterns, helping identify organic compounds.
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Esterification
Esterification is a reaction between a carboxylic acid and an alcohol, catalyzed by acid, to form an ester and water, following Fischer esterification.
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Resonance energy
Resonance energy is the stabilization energy due to electron delocalization, as in benzene, which is about 36 kcal/mol more stable than a hypothetical non-resonant structure.
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Tautomerism
Tautomerism is the phenomenon where a compound exists in two isomeric forms that interconvert rapidly, like keto-enol tautomerism in acetone.
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Conformational isomer
Conformational isomers are different spatial arrangements due to rotation around single bonds, such as chair and boat forms of cyclohexane, affecting stability.
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Hybridization
Hybridization describes the mixing of atomic orbitals to form new hybrid orbitals, like sp3 in alkanes, which determines molecular geometry and bonding.