It seems one of the best-kept secrets of JSON: When exactly can you leave out the quotes around a string – and what quotes (single or double) are you supposed to use anyway?
Never. Dropping the quotes is legal in literals in JavaScript code, but illegal in JSON. Strings are always quoted, and keys are always strings. "Lax JSON" parsers may exist that accept illegal JSON with unquoted keys or other things, but that doesn't change the fact that it is illegal JSON as such, and no JSON parser is required to accept it.