Vitalism
Explication
Vitalism was the belief that organic compounds could arise only in living organisms through a vital force. Wöhler’s urea synthesis later disproved this claim.
Wöhler’s synthesis of urea from ammonium cyanate
Explication
In 1828, Wöhler made urea from ammonium cyanate, demonstrating that organic compounds could be synthesized without a living organism. This directly challenged vitalism.
Lewis structure
Explication
A Lewis structure uses dots or lines for shared electron pairs and shows lone pairs on individual atoms. Bond-line and condensed formulas do not display that electron detail.
Carbon atoms are implied and hydrogen atoms are omitted
Explication
Bond-line structures omit carbon and hydrogen symbols because they are implied by valency. Heteroatoms are the ones written explicitly.
A compound containing only carbon and hydrogen atoms
Explication
Hydrocarbons contain only carbon and hydrogen. Compounds with oxygen or other elements are not hydrocarbons.
It contains at least one multiple bond and can add hydrogen under suitable conditions
Explication
Unsaturated hydrocarbons have one or more multiple bonds, so they can add hydrogen. The presence of only single bonds describes saturated compounds instead.
CnH2n+2
Explication
Alkanes are saturated hydrocarbons with the general formula CnH2n+2. The other formulas correspond to cycloalkanes, alkenes, or unrelated compounds.
The central carbon is bonded to four other carbons
Explication
Neo-alkanes have a central carbon attached to four other carbons. By contrast, iso-alkanes branch near the end of the chain and n-alkanes are continuous chains.
They have the same molecular formula but different atomic connectivity
Explication
Constitutional isomers share a molecular formula but differ in how their atoms are connected. Because of that, they can have different physical properties.
They are likely structural isomers
Explication
If compounds have the same molecular formula but different boiling points, that supports structural isomerism. Physical property differences are a key clue that connectivity is different.
2-methylbutane
Explication
The longest chain has four carbons, so the parent name is butane, and the methyl substituent is on carbon 2. The other options either use the wrong chain length or the wrong substituent position.
Choose the longest chain and number it from the end nearest the first branch
Explication
Alkane nomenclature uses the longest continuous carbon chain as the parent and numbers it to give substituents the lowest possible numbers. The other choices violate standard naming rules.
It is a resonance hybrid of two equivalent Kekulé structures
Explication
Benzene is represented as a resonance hybrid of two equivalent Kekulé structures, reflecting equal bond character in the ring. The alternating single-and-double-bond picture is an older model, not the modern one.
They have a lower hydrogen-to-carbon ratio than typical aliphatic hydrocarbons
Explication
Aromatic hydrocarbons are characterized by a relatively low H:C ratio, with benzene as a classic example. They are not defined by saturation, triple bonds, or the presence of heteroatoms.
Methane
Explication
Natural gas consists chiefly of methane, typically more than 90%. The other hydrocarbons may be present, but only in smaller amounts.
It is a dark, viscous mixture of fossil hydrocarbons that must be separated into useful fractions
Explication
Crude oil is a complex fossil hydrocarbon mixture that is refined by separation into fractions. The other options describe unrelated materials or the wrong natural source.
Gasoline
Explication
Gasoline is listed as the fraction with roughly C5 to C10 hydrocarbons and a 40 to 200 °C boiling range. Natural gases are lighter, while lubricating oils and waxes are heavier.
The behavior of 2,2,4-trimethylpentane
Explication
The octane scale uses 2,2,4-trimethylpentane as the 100 reference point and heptane as the 0 reference point. Octane number measures antiknock performance, not sulfur content or aromatic percentage.
Breaking large hydrocarbon molecules into smaller ones by heat or catalysts
Explication
Cracking splits larger hydrocarbons into smaller molecules and may be thermal or catalytic. Fractional distillation separates mixtures, while combustion and coal burning are different processes.
To heat coal in the absence of air and obtain volatile products such as coal gas and coal tar
Explication
Destructive distillation means heating coal without air, producing volatile products, coke, and coal tar. It is not a combustion process and is unrelated to crude-oil fractionation.
Mémorisez les réponses avec 20 flashcards sur Organic Hydrocarbon Fundamentals.
Vitalism — idea?
Organic compounds only from living organisms.
Wöhler urea synthesis — significance?
Disproved vitalism by making urea from inorganic materials.
Catenation — ability?
Atoms of the same element bond to form chains and rings.
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