Derivatives and combined analytical constraints
導入済み| English | 意味 |
|---|---|
| retention time/rɪˈtenʃn taɪm/ | 保持時間 |
| co-elution | 共溶出 |
| integrated | 積分の |
| provenance/ˈpruːvnəns/ | 由来記録 |
One matching result is not a full identification
- A GC peak with the same retention time 保留时间 as a reference can still come from a different compound or hide co-elution 共洗脱.
- Combine separation evidence with formula, spectra and chemical behaviour.
Retain the acyl carbon in reactions
- Ethanoyl chloride with ethanol gives ethyl ethanoate and HCl. With excess ammonia it gives ethanamide and NH₄Cl.
- Acid ester hydrolysis gives acid and alcohol reversibly. Alkaline hydrolysis gives carboxylate salt and alcohol, driving the reaction toward products.
Hot aqueous NaOH hydrolyses ethyl ethanoate. Which organic products form?
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
In alkaline solution the acid product is present as carboxylate salt.
Count environments and assign proton sets
- Carbon-13 NMR counts distinct environments. Symmetry makes propanone have two signals although it has three carbons.
- Ethyl ethanoate gives a 3H acyl-methyl singlet, 2H OCH₂ quartet and 3H terminal-methyl triplet in the simple model.
For C₂H₆O, using C = 12.0000, H = 1.0078 and O = 15.9949 gives 2×12.0000 + 6×1.0078 + 15.9949 = 46.0417.
Three carbon atoms always give three carbon-13 NMR signals.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
Equivalent carbons give the same signal, as the two methyl carbons do in propanone.
An ethyl group commonly gives a 3H triplet and a 2H _____.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
The CH₂ protons are split by three equivalent neighbouring methyl H atoms in the simple n+1 model.
Combine exact and relative information
- Integrated 积分的 proton areas give ratios; splitting gives neighbour evidence; supplied shifts support environments. Exchangeable OH/NH peaks may not follow simple splitting.
- Accurate masses distinguish some formulae with the same nominal mass. Use all given precise atomic masses before rounding.
Interpret the separation limits
- Rf is spot distance divided by solvent-front distance from the same baseline, without units. Compare references under matched conditions.
- GC–MS supplies mass and fragment evidence for separated components. Standards, blanks and sample provenance 来源记录 strengthen a forensic or drug-test interpretation.
“One chromatographic peak proves purity” is false. Multiple components may co-elute.
Make every proposed structure satisfy all observations and state which alternatives the evidence cannot exclude.
A TLC spot travels 3.6 cm and solvent front 6.0 cm from the baseline. Find Rf.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Rf = 3.6/6.0 = 0.60, with no units.
Which two actions strengthen a retention-time identification?
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Matched references and independent mass evidence reduce ambiguity; provenance and co-elution limits still matter.