Radical Reactions, Alcohols and an Introduction to Spectroscopy: every key term you need (+ practice quiz)
25 flashcard terms for Organic Chemistry I Topic 8, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 15-question quiz — free, no account needed.
A species with an unpaired electron, drawn with a single-headed arrow notation for electron movement. It is electron deficient yet neutral, and it reacts to pair that lone electron.
Radical initiation step
The stage that generates the first radicals, usually by light or heat splitting a weak bond such as the one in a halogen molecule or a peroxide.
Radical propagation step
A step that consumes one radical and produces another, so the chain continues. A working chain requires two complementary propagation steps that sum to the overall reaction.
Radical termination step
Combination of two radicals to give a closed-shell product. It destroys chain carriers, so it is undesirable during synthesis but unavoidable as reagents are consumed.
Radical stability order
Tertiary is more stable than secondary, then primary, then methyl, and allylic or benzylic positions beat all of them because the odd electron is delocalized into a pi system.
Allylic bromination
A brominating agent that maintains a very low bromine concentration selectively substitutes at the position next to a double bond rather than adding across the pi bond.
Radical halogenation selectivity
Bromination strongly prefers the weakest carbon-hydrogen bond because its abstraction step is endothermic and product-like, while chlorination is fast and much less discriminating.
Peroxide effect
Adding a peroxide switches hydrogen bromide addition to a radical chain, so bromine ends up on the less substituted carbon, the opposite of the ionic outcome.
Sodium borohydride
A mild hydride source that reduces aldehydes and ketones to alcohols but leaves esters and carboxylic acids untouched, and it tolerates alcohol solvents.
Lithium aluminum hydride
A powerful hydride reagent that reduces esters, acids, and amides as well as simple carbonyls. It reacts violently with water, so a separate workup step is required.
Grignard reagent
An organomagnesium halide made from an alkyl halide and magnesium metal in dry ether. Its carbon is strongly nucleophilic and behaves as if it carried negative charge.
Grignard addition to a carbonyl
The nucleophilic carbon attacks the carbonyl carbon to form a new carbon-carbon bond, and acidic workup then protonates the resulting alkoxide to give an alcohol.
Grignard incompatibility
Any acidic hydrogen destroys the reagent by protonating it, so alcohols, water, carboxylic acids, and terminal alkynes cannot be present in the same flask.
Thionyl chloride
Converts an alcohol into an alkyl chloride by turning the hydroxyl into an excellent leaving group, with gaseous byproducts that drive the reaction forward.
Phosphorus tribromide
Converts an alcohol into an alkyl bromide under mild conditions with inversion at the reacting carbon, avoiding the rearrangements common with strong acid routes.
Pyridinium chlorochromate
A mild chromium reagent used in anhydrous conditions that stops the oxidation of a primary alcohol at the aldehyde instead of carrying on to the acid.
Oxidation level of alcohols
Primary alcohols can go to aldehydes and then acids, secondary alcohols stop at ketones, and tertiary alcohols resist oxidation because they have no hydrogen on the carbinol carbon.
Williamson ether synthesis
An alkoxide displaces a leaving group from an unhindered primary carbon to give an ether. Choosing which partner supplies the alkoxide matters greatly for the yield.
Infrared spectroscopy
A technique measuring the frequencies at which bonds stretch and bend. Strong dipole changes give strong bands, and the region above about fifteen hundred wavenumbers identifies functional groups.
Carbonyl stretching band
An intense absorption near seventeen hundred wavenumbers that reliably announces an aldehyde, ketone, ester, or acid. Its exact position distinguishes among those groups.
Hydroxyl stretching band
A broad absorption between about thirty-two hundred and thirty-six hundred wavenumbers. Hydrogen bonding is what broadens it, and a carboxylic acid version is broader still.
Molecular ion peak
The mass spectrum signal from the intact molecule minus one electron, giving the molecular mass directly when the ion survives long enough to be detected.
Halogen isotope pattern
Bromine produces two peaks of nearly equal height two mass units apart, while chlorine produces a pair in roughly a three to one ratio, revealing which halogen is present.
Proton chemical shift
The position of a signal relative to a reference, driven by the electron density around the nucleus. Nearby electronegative atoms and pi systems push signals downfield.
Spin-spin splitting
Neighboring nonequivalent hydrogens split a signal into a number of lines one greater than their count, which reveals how many hydrogens sit on adjacent carbons.