Chemical data of Lactic acid

I've struggled with How Mathematica expects the end-user to interact with knowledge databases for quite some time. While this solution is likely not universal, it has been reasonably successful for many of my searches.

Using CTRL= to perform a free-form Wolfram Language input followed by using CanonicalName typically provides the appropriate string to conduct additional property searches:

Jason B. notes in the comments that one can obtain the same information programmatically through Interpreter["Chemical"]["lactic acid"]. I've included it in the answer in case the comments get removed in the future.

ChemicalData[Entity["Chemical", "MilkAcid"], "MoleculePlot"]

or

Entity["Chemical", "MilkAcid"];

ChemicalData[%,"MolecularPlot"]

What has been missed in previous answers is that one should have tried entering the name of the chemical under consideration in camel case:

ChemicalData["LacticAcid"]
   {Entity["Chemical", "MilkAcid"], Entity["Chemical", "LPlusLacticAcid"], 
    Entity["Chemical", "DLLacticAcid"], Entity["Chemical", "PolyDLLactide"],
    Entity["Chemical", "PolyLLactide"]}

which returns a bunch of matches. Note that the first entry corresponds to the "milk acid" entity featured in bob's answer. The next two entries correspond to the natural enantiomer of lactic acid and the racemic form, which may also be of interest.

Similarly, evaluating ChemicalData["LacticAcid", "MoleculePlot"] will show the expected plots, at least for the first three entries:

ChemicalData["LacticAcid", "MoleculePlot"] // GraphicsRow

The OP almost got it by trying out the IUPAC name, what was not done was to write the name in the expected camel case:

ChemicalData["2HydroxypropanoicAcid"]
   {Entity["Chemical", "MilkAcid"], Entity["Chemical", "DLLacticAcid"],
    Entity["Chemical", "PolyDLLactide"]}